[16.0][ADD] base_external_system_http

[ntsirintanis]

This module provides an HTTP(S) adapter for the base_external_system framework.

It allows Odoo to communicate with external systems over HTTP using a consistent
adapter interface, supporting GET, POST and PUT requests, endpoint resolution,
and connection testing.

The adapter itself acts as the client and is yielded via the standard
system.client() context manager.

[ntsirintanis]

@thomaspaulb @NL66278

[NL66278]

@ntsirintanis please base your changes on the original PR. It is very difficult for me what changes you actually made, even apart from doing away with the commit history of this module. #377

[ntsirintanis]

@ntsirintanis please base your changes on the original PR. It is very difficult for me what changes you actually made, even apart from doing away with the commit history of this module. #377

This MR contains an obsolete version of base_external_system and it is standalone on its own, so we should not do anything there. What I am going to do is cherry-pick a single commit, this one e4a1704, and push it here