- Adds an STS API `AssumeRoleWithCustomToken` that can be used to
authenticate via the Id. Mgmt. Plugin.
- Adds a sample identity manager plugin implementation
- Add doc for plugin and STS API
- Add an example program using go SDK for AssumeRoleWithCustomToken
- This change renames the OPA integration as Access Management Plugin - there is
nothing specific to OPA in the integration, it is just a webhook.
- OPA configuration is automatically migrated to Access Management Plugin and
OPA specific configuration is marked as deprecated.
- OPA doc is updated and moved.
