Filter `date` does not work and should be changed to `creation`

[dgruano]

Hi there!

The index API documentation mentions the filter date as a way to retrieve results based on date:

oc_api/src/ramose.py

Line 208 in aca3d23

2. `filter=<field_name>:<operator><value>`: only the rows compliant with `<value>` are kept in the result set. The parameter `<operation>` is not mandatory. If `<operation>` is not specified, `<value>` is interpreted as a regular expression, otherwise it is compared by means of the specified operation. Possible operators are "=", "<", and ">". For instance, `filter=title:semantics?` returns all the rows that contain the string "semantic" or "semantics" in the field `title`, while `filter=date:>2016-05` returns all the rows that have a `date` greater than May 2016.

However, this does not work, as date is not a valid field (note that the required filter pattern should be filter=<field_name>:<operator><value> ).

This should actually be changed to creation which is the actual field name containing the creation date.

For reference, here is an example:

(1) Filter by date:

Request URL:

https://api.opencitations.net/index/v2/citations/doi:10.1093/nar/gkt006?filter=date:%3E2020

First result:

    {
        "oci": "061902621438-061501344591",
        "citing": "omid:br/061902621438 doi:10.1038/srep34838 openalex:W2529308621 pmid:27708423",
        "cited": "omid:br/061501344591 doi:10.1093/nar/gkt006 openalex:W2048194168 pmid:23335781",
        "creation": "2016-10-06",
        "timespan": "P3Y8M19D",
        "journal_sc": "no",
        "author_sc": "no"
    },

(2) Filter by creation:

Request URL:

https://api.opencitations.net/index/v2/citations/doi:10.1093/nar/gkt006?filter=creation:%3E2020

First result:

    {
        "oci": "061702215634-061501344591",
        "citing": "omid:br/061702215634 doi:10.7717/peerj.8548 openalex:W3005728317 pmid:32095365",
        "cited": "omid:br/061501344591 doi:10.1093/nar/gkt006 openalex:W2048194168 pmid:23335781",
        "creation": "2020-02-12",
        "timespan": "P7Y0M26D",
        "journal_sc": "no",
        "author_sc": "no"
    },