Duplicate person entries due to case sensitivity in email addresses

[Aidajafarbigloo]

In the persons table, when two rows have the same given name and family name, they may be treated as the same person if the email addresses match. However, if the email addresses differ only by capitalization (e.g., User@example.com vs. user@example.com), the tool treats them as two separate persons, and we have duplicated entries.

Expected behavior:
Email addresses should be treated in a case-insensitive manner so that capitalization differences do not create duplicate person entries.

[Aidajafarbigloo]

Partially solved in #248

[Aidajafarbigloo]

When adding a new email to an existing row, it does not recognize the email as a duplicate if the same email address is entered with different letter casing (uppercase or lowercase).