Support Bitbucket Self-hosted

[hywax]

Describe the feature

Hi! We use Bitbucket Self-hosted at work. But we don't support Self-hosted in giget.

Additional information

• [X] Would you be willing to help implement this feature?

[sn00k]

We would also be very interested in this in our team at work, it's the only blocker for us to adopt this straight away.

[hywax]

Looking forward to a review from @pi0