Make the bearer token optional for API callbacks

[jimleroyer]

Description

As a user of Notify,
I want the bearer token from the API callback to be optional,
So that I can leverage my Azure SAS authentication without getting impeded by the bearer token authentication.

WHY are we building?

To support authentication use cases that only requires the URL and no bearer token necessary.

WHAT are we building?

Making the bearer token field optional in the UI, the database and the application's model.

VALUE created by our solution

More authentication mechanism supported by Notify.

Redflags

Potentially, that might make some users not use a bearer tokens when they should. That will not minimize security from Notify side though as this is user's responsibility to protect their endpoints.

Acceptance Criteria** (Definition of done)

• The bearer token is now optional in the UI.
• The bearer token is now optional in the database.
• Unit tests cover the new scenario.

QA Steps

• Register a service API callback with no bearer token.
• Confirm with user reporting the issue that it works fine.

Additional info

• This was reported via this Freshdesk ticket.
• There is an exploratory PR that was opened in API to assess how much work that would require.