Feature enable/disable is not supported per user

[AndriiZhydkykh]

Requirement
Core features must be enable-/disable-able per user/group:
Internet search (web browsing)
Code execution (code interpreter)
Artificial limitation of context length for cost control

Actual Result
Features can be enabled/disabled only at group (team) level.
Per-user configuration is not available.

[yannickmonney]

Implementation PR: #1375