fix: enable FeatureHighAvailability if it is licensed (#10834)

fixes #10810

The tailnet coordinators don't depend on replicasync, so we can still enable HA coordinators even if the relay URL is unset.

The in-memory, non-HA coordinator probably has lower latency than the PG Coordinator, since we have to query the database, so enterprise customers might want to disable it for single-replica deployments, but this PR default-enables the HA coordinator.  We could add support later to disable it if anyone complains. Latency setting up connections matters, but I don't believe the coordinator contributes significantly at this point for reasonable postgres round-trip-time.

codersdk/deployment.go

@@ -95,6 +95,7 @@ func (n FeatureName) AlwaysEnable() bool {
 		FeatureExternalProvisionerDaemons: true,
 		FeatureAppearance:                 true,
 		FeatureWorkspaceBatchActions:      true,
+		FeatureHighAvailability:           true,
 	}[n]
 }
 

enterprise/coderd/coderd.go

@@ -472,7 +472,6 @@ func (api *API) updateEntitlements(ctx context.Context) error {
 			codersdk.FeatureAuditLog:                   api.AuditLogging,
 			codersdk.FeatureBrowserOnly:                api.BrowserOnly,
 			codersdk.FeatureSCIM:                       len(api.SCIMAPIKey) != 0,
-			codersdk.FeatureHighAvailability:           api.DERPServerRelayAddress != "",
 			codersdk.FeatureMultipleExternalAuth:       len(api.ExternalAuthConfigs) > 1,
 			codersdk.FeatureTemplateRBAC:               api.RBAC,
 			codersdk.FeatureExternalTokenEncryption:    len(api.ExternalTokenEncryption) > 0,