!htp #18919 #19519 New JavaDSL for Akka HTTP (#20518)

* !htt #18919 #19519 Align Java HTTP server DSL with Scala

This commits replaces the Java HTTP server DSL with a Java-8 centric one
which exposes all scala DSL concepts to be usable from Java, including
custom directives, (un)marshallers, rejections, headers, and type safety
for path and query parameters.

* Add RequestContext and RouteResult to Java DSL
fix websockets
WIP bring java docs up to date.
This applies some updates to the root-level documentation

* [htp] Fix java documentation to correctly mention timeouts

Timeouts are configured the same in Java and Scala. Hence, linking to the
scala docs for timeouts from Java.

* =htc fix optionalHeaderValueByType in Java

* =htt #20200 fix java testkit always using NoLogging instead logger

* +htt actually run new javadsl tests, allow overriding config

* =htt improve javadsl test infra with more details when fails

* =htt fix bug in wrong path matcher exposed

* +htp add missing remaining path matcher

* =htp Java DSL cookie tests fixed

* =htt Java DSL ParameterDirectivesTest fixed

Protect the tweets from scalariform

Incorrect response expectations in cache condition directives spec fixed

* =htt Path directives for Java DSL

* +!htt PathMatchers rewritten, made uniform and tests passing

* Bugfix in java reject and a little test-boyscouting

* Revert "Incorrect response expectations in cache condition directives spec fixed"

This reverts commit cd50e89d45db010309f8249b090ea654ebb11c7a.

* +htc HttpAPIsTest is compile time only, not for running
Also, moved from the client package since not strictly a client test.

SecurityDirectives passing

Two faulty tests and two actual bugs.

Fix for cache condition spec not working

* Not sending in Unit instad of the implicit magnet in the test
* HeaderMagnet now works as expected
* Java API added for - and + on DateTime

PetStore example and test fixed

* Annotations to make marshalling work without default constructor
* Made model class immutable

Incorrect tests fixed

Some scaladoc boyscouting as bonus

* =htt RequestValTest sprinkled out across multiple directive tests

Client ip extraction test with incorrect header name fixed.

* =htt Incorrect CodingDirectivesTest fixed.

* =htt Bugfix for Java Unmarshaller.firstOf and fixes to JavaRouteTest

* =htt MarshallerTest fixed

* Missing seal signature added to JavaDSL
* More consistent (with Scala) test kit setup for Java
* missing Javadocs added
* Thread.sleep in default exception handler removed

* =htt copy directive docs, prepare for finishing it up

* +htt SecurityDirectives.authorize variants and test coverage added

* +htt Custom headers in Java DSL

* =htt WIP on java docs

* +htp add missing parameterOrDefault directive
Fixed a lot of doc warnings

* =htc intense progress on javadsl docs

* =htc #20470 Link to issue about docs and fix compile error
compile, migration guide
don't mima check http-experimental

* =htt Java DSL doc warnings fixed.
Only `Could not lex literal_block` ones left now

* =htc fix mima settings

* =doc fix MethodDirectives doc test with custom method

* =htc fix coding directives spec after bad merge

* =htc fix concat being corresponding to route() in javadsl

* =htt Disable consistency check for route/concat as it fails only on ci server

* !htt Minor fixes to PathMatchers

akka-docs/rst/java/http/routing-dsl/directives/coding-directives/decodeRequest.rst

@@ -0,0 +1,13 @@
+.. _-decodeRequest-java-:
+
+decodeRequest
+=============
+
+Description
+-----------
+
+Decompresses the incoming request if it is ``gzip`` or ``deflate`` compressed. Uncompressed requests are passed through untouched. If the request encoded with another encoding the request is rejected with an ``UnsupportedRequestEncodingRejection``.
+
+Example
+-------
+..TODO: Example snippets for JavaDSL are subject to community contributions! Help us complete the docs, read more about it here: `write example snippets for Akka HTTP Java DSL #20466 <https://github.com/akka/akka/issues/20466>`_.

akka-docs/rst/java/http/routing-dsl/directives/coding-directives/decodeRequestWith.rst

@@ -0,0 +1,13 @@
+.. _-decodeRequestWith-java-:
+
+decodeRequestWith
+=================
+
+Description
+-----------
+
+Decodes the incoming request if it is encoded with one of the given encoders. If the request encoding doesn't match one of the given encoders the request is rejected with an ``UnsupportedRequestEncodingRejection``. If no decoders are given the default encoders (``Gzip``, ``Deflate``, ``NoCoding``) are used.
+
+Example
+-------
+TODO: Example snippets for JavaDSL are subject to community contributions! Help us complete the docs, read more about it here: `write example snippets for Akka HTTP Java DSL #20466 <https://github.com/akka/akka/issues/20466>`_.

akka-docs/rst/java/http/routing-dsl/directives/coding-directives/encodeResponse.rst

@@ -0,0 +1,19 @@
+.. _-encodeResponse-java-:
+
+encodeResponse
+==============
+
+Description
+-----------
+
+Encodes the response with the encoding that is requested by the client via the ``Accept-Encoding`` header or rejects the request with an ``UnacceptedResponseEncodingRejection(supportedEncodings)``.
+
+The response encoding is determined by the rules specified in RFC7231_.
+
+If the ``Accept-Encoding`` header is missing or empty or specifies an encoding other than identity, gzip or deflate then no encoding is used.
+
+Example
+-------
+TODO: Example snippets for JavaDSL are subject to community contributions! Help us complete the docs, read more about it here: `write example snippets for Akka HTTP Java DSL #20466 <https://github.com/akka/akka/issues/20466>`_.
+
+.. _RFC7231: http://tools.ietf.org/html/rfc7231#section-5.3.4

akka-docs/rst/java/http/routing-dsl/directives/coding-directives/encodeResponseWith.rst

@@ -0,0 +1,22 @@
+.. _-encodeResponseWith-java-:
+
+encodeResponseWith
+==================
+
+Description
+-----------
+
+Encodes the response with the encoding that is requested by the client via the ``Accept-Encoding`` if it is among the provided encoders or rejects the request with an ``UnacceptedResponseEncodingRejection(supportedEncodings)``.
+
+The response encoding is determined by the rules specified in RFC7231_.
+
+If the ``Accept-Encoding`` header is missing then the response is encoded using the ``first`` encoder.
+
+If the ``Accept-Encoding`` header is empty and ``NoCoding`` is part of the encoders then no
+response encoding is used. Otherwise the request is rejected.
+
+Example
+-------
+TODO: Example snippets for JavaDSL are subject to community contributions! Help us complete the docs, read more about it here: `write example snippets for Akka HTTP Java DSL #20466 <https://github.com/akka/akka/issues/20466>`_.
+
+.. _RFC7231: http://tools.ietf.org/html/rfc7231#section-5.3.4

akka-docs/rst/java/http/routing-dsl/directives/coding-directives/index.rst

@@ -0,0 +1,14 @@
+.. _CodingDirectives-java:
+
+CodingDirectives
+================
+
+.. toctree::
+   :maxdepth: 1
+
+   decodeRequest
+   decodeRequestWith
+   encodeResponse
+   encodeResponseWith
+   requestEncodedWith
+   responseEncodingAccepted

akka-docs/rst/java/http/routing-dsl/directives/coding-directives/requestEncodedWith.rst

@@ -0,0 +1,15 @@
+.. _-requestEncodedWith-java-:
+
+requestEncodedWith
+==================
+
+Description
+-----------
+
+Passes the request to the inner route if the request is encoded with the argument encoding. Otherwise, rejects the request with an ``UnacceptedRequestEncodingRejection(encoding)``.
+
+This directive is the building block for ``decodeRequest`` to reject unsupported encodings.
+
+Example
+-------
+TODO: Example snippets for JavaDSL are subject to community contributions! Help us complete the docs, read more about it here: `write example snippets for Akka HTTP Java DSL #20466 <https://github.com/akka/akka/issues/20466>`_.

akka-docs/rst/java/http/routing-dsl/directives/coding-directives/responseEncodingAccepted.rst

@@ -0,0 +1,13 @@
+.. _-responseEncodingAccepted-java-:
+
+responseEncodingAccepted
+========================
+
+Description
+-----------
+
+Passes the request to the inner route if the request accepts the argument encoding. Otherwise, rejects the request with an ``UnacceptedResponseEncodingRejection(encoding)``.
+
+Example
+-------
+TODO: Example snippets for JavaDSL are subject to community contributions! Help us complete the docs, read more about it here: `write example snippets for Akka HTTP Java DSL #20466 <https://github.com/akka/akka/issues/20466>`_.