XYZ-37: Advanced Permissions Phase 1 Backend. (#8159)

* XYZ-13: Update Permission and Role structs to new design.

* XYZ-10: Role store.

* XYZ-9/XYZ-44: Roles API endpoints and WebSocket message.

* XYZ-8: Switch server permissions checks to store backed roles.

* XYZ-58: Proper validation of roles where required.

* XYZ-11/XYZ-55: Migration to store backed roles from policy config.

* XYZ-37: Update unit tests to work with database roles.

* XYZ-56: Remove the "guest" role.

* Changes to SetDefaultRolesFromConfig.

* Short-circuit the store if nothing has changed.

* Address first round of review comments.

* Address second round of review comments.

model/permission_test.go

@@ -0,0 +1,18 @@
+package model
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// This is a test to ensure that we don't accidentally add more permissions than can fit
+// in the database column for role permissions.
+func TestPermissionsLength(t *testing.T) {
+	permissionsString := ""
+	for _, permission := range ALL_PERMISSIONS {
+		permissionsString += " " + permission.Id
+	}
+
+	assert.True(t, len(permissionsString) < 4096)
+}