update all conformance classes to 1.0.0-rc.1 and fix several extension cc URIs with extra forward-slash

[philvarner]

Related Issue(s):

• Conformance classes inconsistency #371
• Update stac-api-spec version to 1.0.0-rc.1 and add collections conformance class. #366

Description:

• update all the conformance classes to be rc.1
• fix the few extension conformance classes that had an extra / before the #
• add the collections conformance class

PR Checklist:

• Code is formatted and linted (run pre-commit run --all-files)
• Tests pass (run make test)
• Documentation has been updated to reflect changes, if applicable, and docs build successfully (run make docs)
• Changes are added to the CHANGELOG.

[geospatial-jeff]

LGTM! We haven't implemented the changes to transactions extension (#384 and #385) but I don't think that is a big deal (https://github.com/radiantearth/stac-api-spec/blob/master/CHANGELOG.md#changed).

[philvarner]

LGTM! We haven't implemented the changes to transactions extension (#384 and #385) but I don't think that is a big deal (https://github.com/radiantearth/stac-api-spec/blob/master/CHANGELOG.md#changed).

Also PATCH support is missing:

• Transaction Extension missing support for PATCH /collections/{collectionId}/items/{featureId} endpoint #375

To clarify,

• Transactions Extension: PUT endpoint is incorrect, should be /collections/{c_id}/items/{i_id} #385
  is not a recent change in Txn Ext -- it's always been defined at this path, it's just that the sfapi impl is incorrect. Only
• Transaction Ext: POST and PUT should validate the Item's id and collection match the path's id and collection #384
• is a change for 1.0.0-rc.1.

To the overall point, there is an "attempt" to implement Txn Ext, so it's reasonable to advertise it, even if it isn't entirely conformant.