Core - Add build information to all requests sent by HTTPClient as headers

[kbendick]

The HTTPClientFactory is used to build the HTTP Client that will be used by the REST Catalog.

This PR injects the following two headers into each request, for debugging purposes:

• X-Client-Version
• X-Client-Git-Commit-Short

To test for these headers, TestHTTPClient was updated to use the HTTPClientFactory. The headers, with their expected values, are placed on each expected request, which is an assertion.

Notice that we don't have to add the headers onto the request that is sent, as they are default headers for each request.

This PR needs relies on work in #5237 and needs to be rebased once that is merged.

[kbendick]

Here's a sample of the headers sent for each request, per the mock server tests:

Relevant portions:
X-Client-Git-Commit-Short: "a850705" X-Client-Version: ""Apache Iceberg 0.14.0-SNAPSHOT (commit a850705)"`

We can update these header names or which values are used (as well as where they're placed and how, but I think HTTPClientFactory makes sense).

Probably using the short version of 0.14.0-SNAPSHOT would be just as sufficient for debugging while reducing unnecessary header size. But I'll let others chime in.

The headers can technically be overridden via the config header.X-Client-Git-Commit-Short in the configuration, although we can code against that (make it a reserved property) if desired.

   "headers" : {
      "Accept" : [ "application/json" ],
      "Content-Type" : [ "application/json" ],
      "X-Client-Git-Commit-Short" : [ "a850705" ],
      "X-Client-Version" : [ "Apache Iceberg 0.14.0-SNAPSHOT (commit a8507057f778efba6f1750ae814749f52a4cd7bc)" ],
      "Authorization" : [ "Bearer auth_token" ],
      "Accept-Encoding" : [ "gzip, x-gzip, deflate" ],
      "Host" : [ "127.0.0.1:1080" ],
      "Connection" : [ "keep-alive" ],
      "User-Agent" : [ "Apache-HttpClient/5.1 (Java/11.0.15)" ],
      "content-length" : [ "0" ]
    }

[kbendick]

These don't really need to be set because HTTPClientFactory isn't used here - the underlying JDBC client is what builds this.

We can however still override the version etc by sending back a configuration property of header.X-Client-Version with the desired value to be used as the value (though I don't see any reason to do that).

[kbendick]

We add the headers that we expect to see as assertions on the mock request. The actual HTTPClient is used, generated by the HTTPClientFactory, which injects the headers.

If requests are not generated which have these headers, they will not match and the assertion of this mock request will fail.

Notice that we didn't have to add the request headers anywhere else (like we do with Authorization elsewhere in this test suite when generating the actual requests on the updated line 205). That signifies that the headers are added automatically if the HTTPClient is created via HTTPClientFactory.

[rdblue]

Thanks, @kbendick!