AnnotationDTO: `content` Column

[luniki]

• Please add a column named content to the AnnotationDTO. It contains a JSON encoded String.
• Add this column in AnnotationDTO#toJSON.

In the backend this column should be handled as a blackbox. The backend gets a string out of a request, stores it in the database, retrieves it from the database.

[luniki]

content should be handled the same way as tags and settings. Both fields contain JSON encoded in a string.

[JulianKniephoff]

I would even argue that if we go this route, we should just merge settings in there, or rather into the appropriate subobjects of that. :thinking:

The same could be said about tags, but seeing that this is never used anywhere, I would rather argue to get rid of tags. :sweat_smile:

Opinions?

[luniki]

see #377