[Bug Report] Performer merge option doesn't transfer most details

[DogmaDragon]

Describe the bug
When merging performers, most details are not transferred. Only image, aliases are transferred, which can lead to lost metadata.

In provided example test performer 1 is being merged into test performer 2. No details are being transferred except for primary name (as alias), alias and image. All other details are being lost. See screenshots below.

To Reproduce
Steps to reproduce the behavior:

1. Open performer profile.
2. Click merge and select performer profile to merge.
3. Confirm merge.
4. See no details being transferred.

Expected behavior
For empty single-value fields in the source profile they should be just filled.
For conflicting single-value fields, marking them and offering a way to resolve should be ideally added.
For multi-value fields either empty or existing, they should just be added in addition.

Screenshots