Compound Documents rework: in-process includes, finer-grained config, stronger security and descriptive meta

#118 Add page for projects that are using the framework already
#203 OAS: Add Swagger example in addition to Redoc
#208 CD: Fetch only what was explicitly requested, not the entire tree
#210 CD: same-app includes are fetched from a host taken from the client's Host header
#211 CD: primary resources are repeated in included
#212 CD: include requests break on unencoded query parameters
#213 CD: consistent handling of failed includes via errorStrategy and the shared error handler registry
#214 CD: say which included resources are missing, and why, in partial responses under errorStrategy: IGNORE
#215 CD: capture the primary response reliably, and enforce include limits per the spec instead of cutting silently
#216 CD: Return 400 for include paths with unknown relationship names, at any position in the path, in core and the CD plugin
#217 CD: forward only safe headers, send credentials only to trusted services, and put all per-type settings under mapping
#218 CD and OAS: take configuration from the registered plugin and JsonApi4j instead of servlet-context copies, plus small cleanups
#220 CD: resolve same-app includes in-process, with per-type transport (IN_PROCESS | HTTP)
#221 Use JSON:API member name constants everywhere possible

More info: #222