HttpClient: send AddVariable params as query string on GETs and read them on the server

[iroqueta]

Summary

Two related fixes for AddVariable usage on GET requests.

Client side (HttpClientJavaLib + GXHttpClient)

On GET, variables added with AddVariable were serialized as a multipart body. Servers, proxies and CDNs ignore the body of a GET so the values never reached the destination. They now go to the URL query string, URL-encoded in UTF-8.

POST/PUT/DELETE keep using the body as before.

Server side (HttpContextWeb)

HttpRequest.GetVariable() consulted only the request body. On a GET this body is empty so values sent via the query string were invisible. Now, only on GET, if the body parsed empty we fall back to the query string.

POST and any other verb are unchanged: the body still has precedence and the query string is not consulted.

Compatibility

Case	Before	After
Client: GET with AddVariable	Variables in multipart body (ignored by servers)	Variables in ?k=v URL
Client: POST with AddVariable	Multipart body	Unchanged
Server: GET with ?k=v, empty body	GetVariable() returns ""	Returns the query-string value
Server: GET with body urlencoded (rare)	Returns body value	Unchanged (body has precedence)
Server: POST with body urlencoded	Returns body value	Unchanged
Server: POST with ?k=v and body	Returns body value (QS ignored)	Unchanged

Test plan

• In GeneXus, run a proc that does &httpClient.AddVariable("PEPE","HOLA") + Execute("GET", url) and verify in org.apache.http.wire that the URL is url?PEPE=HOLA with no body.
• Run the same with POST and confirm the multipart body is unchanged.
• Call an HTTP proc with ?PEPE=HOLA from a browser and confirm &HttpRequest.GetVariable("PEPE", &v) returns HOLA.
• Send a POST with form-urlencoded body to an HTTP proc and confirm GetVariable keeps reading from the body.

Issue: 208539

[genexusbot]

Cherry pick to beta failed, 1 conflicted file in commit 85180bc

• common/src/main/java/com/genexus/internet/GXHttpClient.java

[genexusbot]

Manual cherry pick to beta success

• 85180bc