Use database for github creds

Add database models that deal with github credentials. This change
adds models for github endpoints (github.com, GHES, etc). This change
also adds code to migrate config credntials to the DB.

Tests need to be fixed and new tests need to be written. This will come
in a later commit.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

database/sql/users.go

@@ -67,6 +67,10 @@ func (s *sqlDatabase) CreateUser(_ context.Context, user params.NewUserParams) (
 		return params.User{}, runnerErrors.NewConflictError("email already exists")
 	}
 
+	if s.HasAdminUser(context.Background()) && user.IsAdmin {
+		return params.User{}, runnerErrors.NewBadRequestError("admin user already exists")
+	}
+
 	newUser := User{
 		Username: user.Username,
 		Password: user.Password,
@@ -129,3 +133,16 @@ func (s *sqlDatabase) UpdateUser(_ context.Context, user string, param params.Up
 
 	return s.sqlToParamsUser(dbUser), nil
 }
+
+// GetAdminUser returns the system admin user. This is only for internal use.
+func (s *sqlDatabase) GetAdminUser(_ context.Context) (params.User, error) {
+	var user User
+	q := s.conn.Model(&User{}).Where("is_admin = ?", true).First(&user)
+	if q.Error != nil {
+		if errors.Is(q.Error, gorm.ErrRecordNotFound) {
+			return params.User{}, runnerErrors.ErrNotFound
+		}
+		return params.User{}, errors.Wrap(q.Error, "fetching admin user")
+	}
+	return s.sqlToParamsUser(user), nil
+}