Encrypt passwords in DB (#1187)

* Encode/Encrypt passwords in DB

* Only decrypts passwords if it is necessary

* Add tests for encryption functions

server/auth.go

@@ -152,7 +152,7 @@ func createAdminUser(ctx context.Context, ds model.DataStore, username, password
 }
 
 func validateLogin(userRepo model.UserRepository, userName, password string) (*model.User, error) {
-	u, err := userRepo.FindByUsername(userName)
+	u, err := userRepo.FindByUsernameWithPassword(userName)
 	if err == model.ErrNotFound {
 		return nil, nil
 	}