Add HMAC protection on /approval endpoint

server/handlers.go

server/oauth2.go

storage/conformance/conformance.go

storage/ent/client/authrequest.go

storage/ent/client/types.go

storage/ent/db/authrequest.go

storage/ent/db/authrequest/authrequest.go

storage/ent/db/authrequest/where.go

storage/ent/db/authrequest_create.go

storage/ent/db/authrequest_update.go

storage/ent/db/migrate/schema.go

storage/ent/db/mutation.go

storage/ent/schema/authrequest.go

storage/etcd/types.go

storage/health.go

storage/kubernetes/types.go

storage/sql/crud.go

storage/sql/migrate.go

storage/storage.go