Ability to add and define relations between series

[PhilippKammann]

Describe your suggested feature

It would be nice if one could add a relation with a relation type between series. With this it would be possible to directly show a prequel, sequel, spin-off, etc. on the series page with clear labels what type the relation has (something that a collection can't do). With the recent addition of text-books for Komga the relations of adaptation and source will also be interesting.

This would work like Kavita's Series Relationships

Another addition afterwards would be to automatically set two-sided relationships (e.g. Setting Series A as prequel to Series B will automatically set Series B as a sequel to Series A

Other details

It would also work like Anilist's relations (example from https://anilist.co/manga/30021/Death-Note/)

Acknowledgements

• [X] I have searched the existing issues and this is a new ticket, NOT a duplicate or related to another open issue.
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• [X] I have updated the app to the latest version.
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