Merge PDF reference documentation into single file

This commit configures the documentation build to merge the entire
reference documentation into a single PDF file.

To achieve that, this commit also fixes duplicate anchors that were
introduced while factoring out common parts of the documentation for MVC
and WebFlux.

Closes gh-28451

framework-docs/src/docs/asciidoc/web/web-uris.adoc

@@ -1,4 +1,4 @@
-[[web-uricomponents]]
+[id={chapter}.web-uricomponents]
 = UriComponents
 [.small]#Spring MVC and Spring WebFlux#
 
@@ -101,12 +101,11 @@ You can shorten it further still with a full URI template, as the following exam
 
 
 
-
-[[web-uribuilder]]
+[id={chapter}.web-uribuilder]
 = UriBuilder
 [.small]#Spring MVC and Spring WebFlux#
 
-<<web-uricomponents, `UriComponentsBuilder`>> implements `UriBuilder`. You can create a
+<<{chapter}.web-uricomponents, `UriComponentsBuilder`>> implements `UriBuilder`. You can create a
 `UriBuilder`, in turn, with a `UriBuilderFactory`. Together, `UriBuilderFactory` and
 `UriBuilder` provide a pluggable mechanism to build URIs from URI templates, based on
 shared configuration, such as a base URL, encoding preferences, and other details.
@@ -194,8 +193,7 @@ that holds configuration and preferences, as the following example shows:
 ----
 
 
-
-[[web-uri-encoding]]
+[id={chapter}.web-uri-encoding]
 = URI Encoding
 [.small]#Spring MVC and Spring WebFlux#
 

framework-docs/src/docs/asciidoc/web/webflux.adoc

@@ -1,4 +1,5 @@
 [[webflux]]
+:chapter: webflux
 = Spring WebFlux
 :doc-spring-security: {doc-root}/spring-security/reference
 
@@ -1199,7 +1200,7 @@ instance. The `View` is then used to render the response.
 
 [[webflux-viewresolution-handling]]
 ==== Handling
-[.small]#<<web.adoc#mvc-handling, Web MVC>>#
+[.small]#<<web.adoc#mvc-viewresolver-handling, Web MVC>>#
 
 The `HandlerResult` passed into `ViewResolutionResultHandler` contains the return value
 from the handler and the model that contains attributes added during request

framework-docs/src/docs/asciidoc/web/webmvc-test.adoc

@@ -1,4 +1,4 @@
-[[testing]]
+[[webmvc.test]]
 = Testing
 [.small]#<<web-reactive.adoc#webflux-test, Same in Spring WebFlux>>#
 

framework-docs/src/docs/asciidoc/web/webmvc-view.adoc

@@ -622,7 +622,7 @@ through https://www.webjars.org/[WebJars].
 
 [[mvc-view-script-integrate]]
 === Script Templates
-[.small]#<<web-reactive.adoc#webflux-script-integrate, WebFlux>>#
+[.small]#<<web-reactive.adoc#webflux-view-script, WebFlux>>#
 
 You can declare a `ScriptTemplateConfigurer` bean to specify the script engine to use,
 the script files to load, what function to call to render templates, and so on.

framework-docs/src/docs/asciidoc/web/webmvc.adoc

@@ -1,4 +1,5 @@
 [[mvc]]
+:chapter: mvc
 = Spring Web MVC
 :doc-spring-security: {doc-root}/spring-security/reference
 

framework-docs/src/docs/asciidoc/web/websocket-intro.adoc

@@ -1,4 +1,4 @@
-[[websocket-intro]]
+[[{chapter}.websocket-intro]]
 = Introduction to WebSocket
 
 The WebSocket protocol, https://tools.ietf.org/html/rfc6455[RFC 6455], provides a standardized
@@ -54,7 +54,7 @@ instructions of the cloud provider related to WebSocket support.
 
 
 
-[[websocket-intro-architecture]]
+[[{chapter}.websocket-intro-architecture]]
 == HTTP Versus WebSocket
 
 Even though WebSocket is designed to be HTTP-compatible and starts with an HTTP request,
@@ -80,7 +80,7 @@ In the absence of that, they need to come up with their own conventions.
 
 
 
-[[websocket-intro-when-to-use]]
+[[{chapter}.websocket-intro-when-to-use]]
 == When to Use WebSockets
 
 WebSockets can make a web page be dynamic and interactive. However, in many cases,