Feature request: allow to specify the client_id #358

When registering a new client, the client_id is auto-generated and not very human-read/write friendly.

There are use cases where users are expected to provide the client_id themselves in UI. Example: Thunderbird Beta provides a "Custom OAuth Configuration" dialog, see below.

I already commented to Mozilla regarding the use of one .well-known URL instead of 3 to 4 free-text fields ( https://bugzilla.mozilla.org/show_bug.cgi?id=1602166#c58 ) but what remains is the client_id as an extra hurdle.

For a public client, being able to choose a user-friendly string such as "MozillaThunderbird" would reduce error-proneness of OAuth2 configuration there.

The suggestion is thus to enrich the Client Registration UI in the SSP admin portal such that a client_id is auto-generated, but make it a suggestion end changeable in UI.