!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/scala/http/common/http-model.rst

@@ -77,7 +77,7 @@ as shown here the Akka HTTP model defines a number of subclasses of ``HttpEntity
 stream of bytes.
 
 
-.. _HttpEntity:
+.. _HttpEntity-scala:
 
 HttpEntity
 ----------
@@ -257,7 +257,7 @@ Transfer-Encoding
   response will not be rendered onto the wire and trigger a warning being logged instead!
 
 Content-Length
-  The content length of a message is modelled via its :ref:`HttpEntity`. As such no ``Content-Length`` header will ever
+  The content length of a message is modelled via its :ref:`HttpEntity-scala`. As such no ``Content-Length`` header will ever
   be part of a message's ``header`` sequence.
   Similarly, a ``Content-Length`` header instance that is explicitly added to the ``headers`` of a request or
   response will not be rendered onto the wire and trigger a warning being logged instead!

akka-docs/rst/scala/http/common/index.rst

@@ -1,4 +1,4 @@
-.. _http-scala-common:
+.. _http-scala-common-scala:
 
 Common Abstractions (Client- and Server-Side)
 =============================================
@@ -19,4 +19,4 @@ which are specific to one side only.
    de-coding
    json-support
    xml-support
-   timeouts
+   timeouts

akka-docs/rst/scala/http/common/timeouts.rst

@@ -1,4 +1,4 @@
-.. _http-timeouts:
+.. _http-timeouts-scala:
 
 Akka HTTP Timeouts
 ==================
@@ -32,7 +32,7 @@ independently for each of those using the following keys::
 Server timeouts
 ---------------
 
-.. _request-timeout:
+.. _request-timeout-scala:
 
 Request timeout
 ^^^^^^^^^^^^^^^
@@ -73,4 +73,4 @@ The connecting timeout is the time period within which the TCP connecting proces
 Tweaking it should rarely be required, but it allows erroring out the connection in case a connection
 is unable to be established for a given amount of time.
 
-it can be configured using the ``akka.http.client.connecting-timeout`` setting.
+it can be configured using the ``akka.http.client.connecting-timeout`` setting.

akka-docs/rst/scala/http/common/xml-support.rst

@@ -28,4 +28,4 @@ Once you have done this (un)marshalling between XML and ``NodeSeq`` instances sh
 
 
 .. _Scala XML: https://github.com/scala/scala-xml
-.. _ScalaXmlSupport: @github@/akka-http-marshallers-scala/akka-http-xml/src/main/scala/akka/http/scaladsl/marshallers/xml/ScalaXmlSupport.scala
+.. _ScalaXmlSupport: @github@/akka-http-marshallers-scala/akka-http-xml/src/main/scala/akka/http/scaladsl/marshallers/xml/ScalaXmlSupport.scala