This PR fixes couple of behaviors with service accounts
- not need to have session token for service accounts
- service accounts can be generated by any user for themselves
implicitly, with a valid signature.
- policy input for AddNewServiceAccount API is not fully typed
allowing for validation before it is sent to the server.
- also bring in additional context for admin API errors if any
when replying back to client.
- deprecate GetServiceAccount API as we do not need to reply
back session tokens
This is to improve responsiveness for all
admin API operations and allowing callers
to cancel any on-going admin operations,
if they happen to be waiting too long.
This PR introduces two new features
- AWS STS compatible STS API named AssumeRoleWithClientGrants
```
POST /?Action=AssumeRoleWithClientGrants&Token=<jwt>
```
This API endpoint returns temporary access credentials, access
tokens signature types supported by this API
- RSA keys
- ECDSA keys
Fetches the required public key from the JWKS endpoints, provides
them as rsa or ecdsa public keys.
- External policy engine support, in this case OPA policy engine
- Credentials are stored on disks
