When adding a deploy key that already exists in the project the existing key would not be returned, resulting in an attempt to create a new one, which in turn caused a 500 error due to an ActiveRecord exception.
When adding a deploy key that exists within another project the key would be joined to the project, but would also attempt to create a new one, which resulted in a 400 error due to the key already existing.
Fixes#22741Fixes#21754
Signed-off-by: Rémy Coutable <remy@rymai.me>
* users (#6878, #3526, #4209): Validation error messages are now exposed through 400 responses, 409 response are sent in case of duplicate email or username
* MRs (#5335): 409 responses are sent in case of duplicate merge request (source/target branches), 422 responses are sent when submiting MR fo/from unrelated forks
* issues
* labels
* projects
