fix(backend): allow a custom API root for backend (#7214)

In case of a self-hosted Gitlab, the API request to get the default
branch always call gitlab.com.
This commit allow to pass a custom API root from the config to the API
call.

Fix #7168

Co-authored-by: Martin Jagodic <jagodicmartin1@gmail.com>

packages/decap-cms-backend-gitlab/src/implementation.ts

@@ -158,6 +158,7 @@ export default class GitLab implements Implementation {
  backend: 'gitlab',
  repo: this.repo,
  token: this.token,
+ apiRoot: this.apiRoot,
  });
  if (defaultBranchName) {
  this.branch = defaultBranchName;

packages/decap-cms-lib-util/src/API.ts

@@ -142,6 +142,7 @@ type Backend = 'github' | 'gitlab' | 'bitbucket';
 type RequestConfig = Omit<RequestInit, 'headers'> &
  HeaderConfig & {
  backend: Backend;
+ apiRoot?: string;
  params?: ParamObject;
  };
 
@@ -199,7 +200,7 @@ export async function apiRequest(
  const { token, backend, ...props } = config;
  const options = { cache: 'no-cache', ...props };
  const headers = await constructRequestHeaders({ headers: options.headers || {}, token });
- const baseUrl = apiRoots[backend];
+ const baseUrl = config.apiRoot ?? apiRoots[backend];
  const url = constructUrlWithParams(`${baseUrl}${path}`, options.params);
  let responseStatus = 500;
  try {
@@ -220,9 +221,10 @@ export async function getDefaultBranchName(configs: {
  backend: Backend;
  repo: string;
  token?: string;
+ apiRoot?: string;
 }) {
  let apiPath;
- const { token, backend, repo } = configs;
+ const { token, backend, repo, apiRoot } = configs;
  switch (backend) {
  case 'gitlab': {
  apiPath = `/projects/${encodeURIComponent(repo)}`;
@@ -236,7 +238,7 @@ export async function getDefaultBranchName(configs: {
  apiPath = `/repos/${repo}`;
  }
  }
- const repoInfo = await apiRequest(apiPath, { token, backend });
+ const repoInfo = await apiRequest(apiPath, { token, backend, apiRoot });
  let defaultBranchName;
  if (backend === 'bitbucket') {
  const {