Cannot use Bitbucket login and importer URL for the same OAuth2 credentials
To configure the new Bitbucket importer for OAuth2, you need to configure the Bitbucket Oauth2 settings with a valid callback URL (e.g. https://gitlab.com/import/bitbucket/callback). Otherwise you hit errors such as gitlab-com/infrastructure#908.
However, the Bitbucket OAuth2 login requires the callback URL to be blank.
Most OAuth2 providers allow you to specify multiple, valid callback URIs, but it seems Bitbucket does NOT support that:
From https://confluence.atlassian.com/bitbucket/oauth-faq-338365710.html:
If you do include the URL in a request it must be appended to the same URL configured in the consumer. So if your consumer callback URL is example.com/add-on the URL in your request must be something similar to example.com/add-on/function. If you don't include the URL in the request we redirect to the callback URL in the consumer.
Do we need to support adding a separate entry for login and import?
/cc:@vsizov @dbalexandre