Epic: Configure and fully support Bitbucket Server

[jldec]

Gitpod users would like to use their own Bitbucket Server to work with Gitpod.

Only Bitbucket Server in version 7.20+ is supported

The experience of registering and connecting users should be at least on parity with private GitLab instances i.e. Bitbucket server integration should be available for both SaaS and and self-hosted so that enterprise users can evaluate the support.

• OAuth integration and Workspace starts with Bitbucket Server v7.20 #7957
• [Bitbucket Server] Add support for installing webhooks and prebuilds with projects #8455
• Include a button icon on the login page for Bitbucket Server provider #8603
• [Bitbucket Server] False permission suggestions on git push  #9062
• Configuration UI to register Bitbucket Server instance #9010
• [Bitbucket Server] Support for PR Contexts #9011
• https://github.com/gitpod-io/website/issues/1939

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Identified follow-ups to be handled outside of this epic.

• [Bitbucket Server] Open in Gitpod uses incorrect URLs for BBS repos previously opened on non-scm contexts #9128
• [Bitbucket Server] Use secret to verify events from webhooks #9012

[geropl]

@AlexTugarev Can you take over cleaning up this epic? E.g., sorting out everything that does not belong here, either by dropping it or by putting it in the "Icebox"?

[jldec]

Thank you @AlexTugarev - Closing this epic now.
Docs landed in https://www.gitpod.io/docs/bitbucket-server-integration