Support Subscriptions API `PATCH` requests

[adamweiner]

Related Issue(s):

Closes #1019

Proposed Changes:

For inclusion in changelog (if applicable):

1. Support Subscriptions API PATCH requests

Diff of User Interface

• Old behavior: N/A
• New behavior: CLI and Python library both support sending PATCH requests to the Subscriptions API

PR Checklist:

• [x] This PR is as small and focused as possible
• [x] If this PR includes proposed changes for inclusion in the changelog, the title of this PR summarizes those changes and is ready for inclusion in the Changelog.
• [x] I have updated docstrings for function changes and docs in the 'docs' folder for user interface / behavior changes
• [x] This PR does not break any examples or I have updated them