[pydantic > 2] [api] Add URL validation to `openid` field

[Leobouloc]

Feature Request

After migration, openid field of BaseXapiOpenIdIFI is of type str (no longer AnyStr). The reason is that AnyUrl in pydantic V2 modifies input strings (adding trailing slashes). This might be correct on a URL standpoint but not necessarily right when using it as an ID, where you would expect strings to be untouched.

It would be nice to add back the initial validation of the URL format (without modifying the string).