Implement gallery tag

[pchalupa]

I would like to add tag to gallery. Tags should be simple strings like: carousel, press, ....

[pchalupa]

Add tag endpoint.

[oliverstasa]

You should be able to add more tags than one - in stead of tag_id (int), it sould be tag_id(array) and expected data entry sould be {1, 2, 3}

[pchalupa]

You should be able to add more tags than one - in stead of tag_id (int), it sould be tag_id(array) and expected data entry sould be {1, 2, 3}

Or we can use join table like on screenshot below. Doctrine has own implementation https://www.doctrine-project.org/projects/doctrine-orm/en/2.8/reference/association-mapping.html#one-to-many-unidirectional-with-join-table