Datetime filter

[GrzegorzPustulka]

Describe the bug
If we make a query using a datetime filter, the query searches for the given date between datetime or start_datetime, end_datetime or start and end_datetime. Below I'm including what the query looks like that the apply_datetime_filter function applies. This seems pointless to me - the user is asking about datetime, not about start_datetime and end_datetime fields. If the user is supposed to be able to search by these fields, they need to be added as separate search fields.

[Bool(filter=[Range(properties__datetime={'gte': '2016-05-23T10:41:10Z', 'lte': '2016-06-23T10:41:10Z'})]), Bool(filter=[Range(properties__start_datetime={'gte': '2016-05-23T10:41:10Z', 'lte': '2016-06-23T10:41:10Z'})]), Bool(filter=[Range(properties__end_datetime={'gte': '2016-05-23T10:41:10Z', 'lte': '2016-06-23T10:41:10Z'})]), Bool(filter=[Range(properties__start_datetime={'lte': '2016-05-23T10:41:10Z'}), Range(properties__end_datetime={'gte': '2016-06-23T10:41:10Z'})])]

To Reproduce
http://127.0.0.1:8080/search?collections=sentinel-2-l2a&datetime=2016-05-23T10:41:10.947Z/2016-06-23T10:41:10.947Z

Expected behavior
The API should return only dates between datetime and datetime, not use start_datetime and end_datetime

[jamesfisher-geo]

Including start_datetime and end_datetime in the datetime search was originally discussed here. Perhaps there can be a solution that works for both of these use-cases

#181

[jonhealy1]

I am open to participating in a conversation about this.

According to the stac-spec, an Item can have a null datetime value but only if start_datetime and end_datetime are set.

Maybe we search on datetime and only fall back to start_datetime and end_datetime, if datetime is set to null. I'm not sure about adding more fields to the /search endpoint. I think it introduces a lot of clutter and we would then be outside of the stac-api-spec.