## [IMP] databases: SSO smooth connection and setup

The aim of this commit is to allow databases_user to be directly connected to
any remote SaaS database to which they have access.
When they click the "connect" button, they will bypass the login screen and be
authenticated automatically.

To achieve this, when a user tries to connect to an accessible SaaS database, we
quickly write their `oauth_uid` to that remote database right before the
connection is initiated.

Before this commit:
A user that was created in the remote db using the create user feature from the
databases module wouldn't get automatically authenticated through the Odoo
OAuth SSO feature.

After this commit:
Users attempting to connect to a SaaS database will be directly connected if the
settings was activated.

task-id: 6071808

## TODO:
- [x] check if we always have oauth_uid for saas db
- [x] think about making the oauth module autoinstall (make a bridge module? or overkill?)
    - We can avoid that and have everything work in place directly, avoiding an inheritance nightmare at installation time. 
- [x] handle cases where it isn't there on both the remote db and the managing one
- [x] write some tests to ensure the code is free from traceback
- [x] add a feature allowing to:
    - [x] add it to all server on which the user has access
    - [x] add it to a specific server (may require the db list view on `res.users`
    - [x] remove the previous and do everything when the user click on "connect"
- [x] would be better to put the code in a new module with auto install => people get auto-install + no "hacky" code.
    - The "hacky" code is not so hacky and with that we can directly advertise the installation of `auth_oauth` in an action
    - [x] add a config in the settings