FIX: trailing slash conflict for api endpoints

[justEhmadSaeed]

Description

Because Django adds a trailing slash at the end of the URL by default, adding a trailing slash to the endpoint makes it throw a 301 error. This PR makes it allow a trailing slash.

Link to the associated ticket: https://2u-internal.atlassian.net/browse/ENT-8526

Testing considerations

• Include instructions for any required manual tests, and any manual testing that has
  already been performed.
• Include unit and a11y tests as appropriate
• Consider performance issues.
• Check that Database migrations are backwards-compatible

Post-review

Squash commits into discrete sets of changes

[pwnage101]

Is the purpose of adding this complexity to improve performance? Are there frontends or other callers which frequently do not pass a trailing slash?

[justEhmadSaeed]

Is the purpose of adding this complexity to improve performance? Are there frontends or other callers which frequently do not pass a trailing slash?

@pwnage101 while publishing subscriptions and other license endpoints on the AWS gateway, we faced the issue of inconsistent trailing slash for endpoints where some endpoints require a trailing slash while others don't. If the developers follow a consistent pattern, they face unexpected redirect errors that are hard to debug and recreate locally.

This PR makes it irrelevant whether you add trailing slash or not, it'll work and the publishing code can remain consistent with their practices.