Enable limited Access Requests feature for the Team plan (gravitation…

…al#29866)

* Add access request monthly limit to Features

* Add a method to retrieve usage of Access Requests

* Verify access request limit when creating

* Remove AccessRequestsFeature.Enabled

Feature is always enabled now, the flag serves no purpose

* Expose usage of access requests in auth server

* Reimplement access request usage using audit log

* Disallow unauthenticated access to resource usage

* Tidy proto structures

* Start enforcing access request limit in auth

* Run GCI

* Add a license header to usage_test.go

* Add missing godoc

* Restructure usage proto per PR comments

* Construct proto.AccessRequestUsage in getARMU

* Reduce log level when encountering an unexpected event

* Simplify return

* Add godoc to GetResourcesUsage in client

* Fix merge mess-ups

* Count all requests, no matter their review state

* Factor out GetAccessRequestMonthlyUsage

* Move out resource usage to its own service

* Validate the limit after dry run is done

Unbreak UI when the limit is up

* Fix imports

* Remove Limit

SearchEvents will default to defaults.EventsIterationLimit

* Rename the service proto

* Add godocs to the gRPC service

* Move resource usage to a dedicated package

* Define single GetUsage rpc for all resource types

* Additions for limited access requests UI rework

* Add a test for GetAccessRequestMonthlyUsage

* Address lint

* Run GCI

* Add licenses where missing

* Expect CTA_UNSPEICIFED rather than `undefined`

* Expect CTA_UNSPECIFIED instead of undefined

api/client/client.go

@@ -58,6 +58,7 @@ import (
 	loginrulepb "github.com/gravitational/teleport/api/gen/proto/go/teleport/loginrule/v1"
 	oktapb "github.com/gravitational/teleport/api/gen/proto/go/teleport/okta/v1"
 	pluginspb "github.com/gravitational/teleport/api/gen/proto/go/teleport/plugins/v1"
+	resourceusagepb "github.com/gravitational/teleport/api/gen/proto/go/teleport/resourceusage/v1"
 	samlidppb "github.com/gravitational/teleport/api/gen/proto/go/teleport/samlidp/v1"
 	trustpb "github.com/gravitational/teleport/api/gen/proto/go/teleport/trust/v1"
 	userloginstatev1 "github.com/gravitational/teleport/api/gen/proto/go/teleport/userloginstate/v1"
@@ -4139,3 +4140,12 @@ func (c *Client) UpsertUserPreferences(ctx context.Context, in *userpreferencesp
 	}
 	return nil
 }
+
+// ResourceUsageClient returns an unadorned Resource Usage service client,
+// using the underlying Auth gRPC connection.
+// Clients connecting to non-Enterprise clusters, or older Teleport versions,
+// still get a plugins client when calling this method, but all RPCs will return
+// "not implemented" errors (as per the default gRPC behavior).
+func (c *Client) ResourceUsageClient() resourceusagepb.ResourceUsageServiceClient {
+	return resourceusagepb.NewResourceUsageServiceClient(c.conn)
+}