Currently, the category filtering for tags endpoint works only with "Platform" value. If we try to use different value, a TypeError is thrown.

We should allow to filter any value, for example:

/api/cost-management/v1/tags/openshift/?filter[category]=whatever

or

/api/cost-management/v1/tags/openshift/?filter[category]=*

Note that Ui currently uses only filter[category]=Platform, which seems to work as expected -> this issue is not urgent.

Steps to reproduce:

1. use the latest esebesto/verify_bucketing iqe branch
2. put breakpoint() into test_api_ocp_on_aws_ingest_multi_sources and run the test
3. once data are ingested, hit:

/api/cost-management/v1/tags/openshift/?filter[category]=whatever

or

/api/cost-management/v1/tags/openshift/?filter[category]=*

You will get TypeError