SSH test fails for Bitbucket ssh key despite successful authentication

[javerberg]

Bug Description

When testing an SSH key against Bitbucket, the connection succeeds but the UI reports failure with the message: "Authentication failed. The key may not be authorized on this host."

Steps to Reproduce

1. Go to Settings > Git Credentials
2. Add an SSH key for Bitbucket
3. Click "Test Connection"
4. Test reports failure despite successful authentication

Expected Behavior

Test should report success when authentication succeeds.

Root Cause

Bitbucket's SSH server returns a different success message than GitHub:

• Bitbucket: Authenticated to bitbucket.org ([x.x.x.x]:22) using "publickey".
• The backend only checks for successfully authenticated, You've successfully authenticated, Welcome to