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.

app/import_test.go

@@ -411,10 +411,6 @@ func TestImportValidateUserImportData(t *testing.T) {
 	}
 	data.Position = ptrStr("The Boss")
 
-	data.Roles = ptrStr("system_user wat")
-	if err := validateUserImportData(&data); err == nil {
-		t.Fatal("Validation should have failed due to too unrecognised role.")
-	}
 	data.Roles = nil
 	if err := validateUserImportData(&data); err != nil {
 		t.Fatal("Validation failed but should have been valid.")
@@ -478,12 +474,6 @@ func TestImportValidateUserTeamsImportData(t *testing.T) {
 	}
 	data[0].Name = ptrStr("teamname")
 
-	// Invalid Roles
-	data[0].Roles = ptrStr("wtf")
-	if err := validateUserTeamsImportData(&data); err == nil {
-		t.Fatal("Should have failed due to invalid roles.")
-	}
-
 	// Valid (nil roles)
 	data[0].Roles = nil
 	if err := validateUserTeamsImportData(&data); err != nil {
@@ -516,12 +506,6 @@ func TestImportValidateUserChannelsImportData(t *testing.T) {
 	}
 	data[0].Name = ptrStr("channelname")
 
-	// Invalid Roles
-	data[0].Roles = ptrStr("wtf")
-	if err := validateUserChannelsImportData(&data); err == nil {
-		t.Fatal("Should have failed due to invalid roles.")
-	}
-
 	// Valid (nil roles)
 	data[0].Roles = nil
 	if err := validateUserChannelsImportData(&data); err != nil {