Merging attributes instead of overwriting them, when importing subscribers

[benstaf]

When importing subscribers, It would be nice to have the option to merge attributes instead of overwriting vs. not-overwriting them

For example, if I have [email protected] with attributes { 'hobbies': ['swimming','cooking']}and then import again [email protected] with attributes { 'hobbies': ['dancing','gardening']} , it would be nice to get [email protected] with attributes { 'hobbies': ['swimming','cooking','dancing','gardening']}

This would be in addition to the option of re-importing vs. skipping existing subscribers, mentioned in issue https://github.com/knadh/listmonk/issues/1883 (still unsolved)

[knadh]

Recursively merging arbitrary attributes in the database, the hobbies[] array for example, is unfortunately not technically feasible.