Add support for sharding across multiple storage accounts for blob containers used for corpus management.
Things to note:
1. Additional storage accounts must be in the same resource group, support the "blob" endpoint, and have the tag `storage_type` with the value `corpus`. A utility is provided (`src/utils/add-corpus-storage-accounts`), which adds storage accounts.
2. If any secondary storage accounts exist, they are used by default for containers.
3. Storage account names are cached in memory the Azure Function instance forever. Upon adding new storage accounts, the app needs to be restarted to pick up the new accounts.
We need to move to supporting data sharding.
One of the steps towards that is stop passing around `account_id`, rather we need to specify the type of storage we need.
This PR makes user information from JWT tokens available as part of a Task.
Included changes:
* Renamed `verify_token` to `call_if_agent`, since this function is specific to agent token verification
* Renames `is_authorized` to `is_agent`, since this function checks if the token is an agent
* Adds support for unmanaged nodes in `is_agent` (see #133 for information)
* Saves the user information from the JWT token on task create as part of `TaskConfig`
Note, `TaskConfig` is what is provided to notification templates. This enables Github issues and ADO work items to tie back to the user that created the task.
Note, while `upn` _usually_ means email for AAD user tokens. If we were going to make use of the email address, we should perform a graph lookup based on the `oid`, but we're not.
