Document HTTP client schema [DBZ-6326]

Migrated from [DBZ-6326](https://issues.redhat.com/browse/DBZ-6326)

h1. Feature request or enhancement

For feature requests or enhancements, provide this information, please:
h2. Which use case/requirement will be addressed by the proposed feature?

The description of the HTTP client for Debezium server doesn't describe the schema of the JSON object that is sent or the accepted status codes.  E.g., I tried returning code 201 but this was flagged as an error as the code only expects 200 or 202.
h2. Implementation ideas (optional)

Provide a detailed description and examples of the JSON payload sent by the HTTP client and its expected response format in the documentation.

Start by locating the Debezium Server HTTP client documentation and the implementation it describes. Document the JSON payload schema and accepted response status codes, including the stated 200, 202, and 201 behavior, with examples; done means the documentation clearly covers the request and response formats.

Written by the indexing model from the issue text.