Just out of curiosity: what is going to happen with the slug?
For instance, I have username rbolte so my public repositories are accessible through https://bitbucket.org/rbolte/some_repo. Is this going to change? And if not, how are we supposed to access the slug? Is that going to be the nickname?
@remie, I am fairly positive that the first part of the slug will change to be the user’s uuid (assuming a user owns the repo). If you enter a uri-encoded uuid as the username now, you will get properly directed to the repo.
Just out of curiosity: will it no longer be possible to see your fellow team members in BitBucket?
https://developer.atlassian.com/bitbucket/api/2/reference/resource/teams/{username}/members
Other tools (read: GitHub) still have this feature in a post-GDPR world. If we are using nicknames / non-identifiable handlers, it should still be possible right?
Actually, it should always be possible if the user consents to it. Given that users get to choose their username/nickname/handle, one could argue that there is no limitation in GDPR that prevents Atlassian from using this (even if it ultimately identifies people) based on the fact that they consent to this.
It would only require Atlassian to A) update their privacy policy and B) provide an easy way to change usernames/nicknames/handles in order for users that object to an identifiable username/nickname/handle.
Many of these GDPR changes seem… not related to GDPR 
Indeed - how can we otherwise create pull-requests via the API?
we have a tool that allows our developers to create pull requests. These now require an account_id when specifying reviewers. So we need a way to convert from a reviewer’s name to their account id.
