gis_data_types can be empty

[m-mohr]

Although for each file format in GET /file_formats a gis_data_types array is required, it is not required to have an item. It should have had a minItems: 1 entry, but hasn't. Thus we can't add it any more as it's also not specified in text anywhere that an entry is required, i.e. it's a breaking change.

ToDo:

• [x] For 1.0.1 we can add a recommendation that at least one item should be given.
• [ ] For 2.0.0 we can add minItems: 1

[soxofaan]

other possible solution: add "if empty: ["other"] is assumed"?

[m-mohr]

@soxofaan That's not really backward compatible, so could only be in 2.0.0. But then we can simply go the clean route that requires a specific item chosen by the back-end.

Nevertheless, I guess implementations will assume that anyway until then.

[m-mohr]

Added the recommendation for API 1.0.1:

It is RECOMMENDED to specify at least one of the data types, which will likely become a requirement in a future API version.