Add grid table

[dtgupta]

This branch adds table:ror_grid to the ROR database when populated. The table contains the ror_id of the organization and the corresponding grid_id (Global Research Identifier Database) for organizations with valid grid_id. The GRID identifier was discontinued in 2021, but it is included for the creation of ground truth for author affiliations. Furthermore, tests were added to ensure the intended working of the code.

[dspinellis]

Thank you for submitting the PR! Please revise as follows:

• [ ] Squash all commits into one.
• [ ] Fix formatting. (The PR currently fails CI. You could see this with the documented pre-commit check.)
• [ ] Add GRID as a field, rather than as a table. In contrast to, say, Wikidata, which might have multiple identifiers (see JSON array below), GRID only has a single identifier in the schema, so the data can be incorporated as a field into the research_organizations table.

           "Wikidata": {
                "preferred": "Q299015",
                "all": [
                    "Q299015",
                    "Q39900929"
                ]
            },
            "GRID": {
                "preferred": "grid.4299.6",
                "all": "grid.4299.6"
            }