Wrong calculation for isPublic field values

[VKTB]

Description:
Sending the following request:
http://{{datagateway-api}}/search-api/documents?filter={"where": {"isPublic": false}, "limit": 5}

returns documents whose isPublic field value is set to False.

At the moment, we set the Document's isPublic field value based on the Investigation's releaseDate ICAT field so if it was released more than 3 years ago then it is set to True. This is wrong because releaseDate is the date it was released publicly so the check should instead be releaseDate <= today. We do the same for the Dataset's isPublic field value but instead use the Dataset's createTime ICAT field which is not the correct field to be used. Instead we need to use the parent Investigation's releaseDate field to determine if it is public or not.

Considering that the Search API uses the anon user when querying ICAT, it means that all the data returned from ICAT is public so if there are any issues with getting the above working then we can just hardcode so that it always return True for the isPublic fields and ignore the filter on those fields.

Acceptance criteria:

• All returned Dataset records have isPublic set to True.
• All returned Document records have isPublic set to True.