default to frequency, else landsat_frequency

[bradleyandrick]

Related Issue(s):

• NA

Proposed Changes:

1. change grid:code aggregation to grid_code_frequency if it is advertised, and if not, then fallback to grid_code_landsat_frequency

NOTE: The UI currently does not gracefully handle if aggregation endpoints do not exist as expected, this fix is dependent on those values being present and is appropriate for the current common use cases. Separate ticket added to refactor handling of STAC endpoints that are configured as if the aggregations exist but the api does not actually contain the values expected in the UI rendering code.

PR Checklist:

• [X] I have added my changes to the CHANGELOG or a CHANGELOG entry is not required.