Extend linter rules (#1300)

- dupword checks for duplicate words in the source code
- durationcheck checks for two durations multiplied together
- forbidigo forbids identifiers
- mirror reports wrong mirror patterns of bytes/strings usage
- misspell finds commonly misspelled English words in comments
- predeclared finds code that shadows one of Go's predeclared identifiers
- thelper detects Go test helpers without t.Helper() call and checks the consistency of test helpers

management/server/http/setupkeys_handler_test.go

@@ -220,6 +220,7 @@ func TestSetupKeysHandlers(t *testing.T) {
 }
 
 func assertKeys(t *testing.T, got *api.SetupKey, expected *api.SetupKey) {
+	t.Helper()
 	// this comparison is done manually because when converting to JSON dates formatted differently
 	// assert.Equal(t, got.UpdatedAt, tc.expectedSetupKey.UpdatedAt) //doesn't work
 	assert.WithinDurationf(t, got.UpdatedAt, expected.UpdatedAt, 0, "")