Contact merge not offered unless one entry has no names

[kib42]

Describe the bug When you have two or more contacts with the same email address the merge functions does not detect them unless one has empty first and last name fields

To Reproduce Steps to reproduce the behavior:

1. Create contact "John Smith" and add email address
2. Create contact "John" and add the same address for "John Smith"
3. Click on "Merge" from the three dots menu
4. Get message "No similar contacts found"

Expected behavior I expect to be offered to merge contacts with the same email address.

[kib42]

The duplicate contacts are detected if one them has the same last name but no first name.

[Jlll1]

The current logic is that contacts are not mergable if their lastnames are not equal and both contacts have at least one name field not empty. I'm not sure that having the contacts being marked as mergable just based on equal email address is correct, some people share an email address, but maybe adding a rule that contacts are mergable when:

• One last name is empty OR last names equal or similar
• One first name is empty OR first names equal or similar
• Email addresses are equal Would suffice?