fix(GHES): respect GITHUB_API_URL when creating installation access token (#38)

Follow up to #36. I just wanted to do some refactoring but turns out I
missed to pass the custom `request` instance to `createAppAuth`. It will
fallback to the default `request` which does not respect
`GITHUB_API_URL`

lib/main.js

@@ -1,16 +1,12 @@
 // @ts-check
 
-import core from "@actions/core";
-import { createAppAuth } from "@octokit/auth-app";
-import { request } from "@octokit/request";
-
 /**
  * @param {string} appId
  * @param {string} privateKey
  * @param {string} repository
- * @param {core} core
- * @param {createAppAuth} createAppAuth
- * @param {request} request
+ * @param {import("@actions/core")} core
+ * @param {import("@octokit/auth-app").createAppAuth} createAppAuth
+ * @param {import("@octokit/request").request} request
  */
 export async function main(
   appId,
@@ -26,6 +22,7 @@ export async function main(
   const auth = createAppAuth({
     appId,
     privateKey,
+    request,
   });
 
   const appAuthentication = await auth({

lib/post.js

@@ -1,11 +1,8 @@
 // @ts-check
 
-import core from "@actions/core";
-import { request } from "@octokit/request";
-
 /**
- * @param {core} core
- * @param {request} request
+ * @param {import("@actions/core")} core
+ * @param {import("@octokit/request").request} request
  */
 export async function post(core, request) {
   const token = core.getState("token");

lib/request.js

@@ -0,0 +1,8 @@
+import { request } from "@octokit/request";
+
+export default request.defaults({
+  baseUrl: process.env["GITHUB_API_URL"],
+  headers: {
+    "user-agent": "actions/create-github-app-token",
+  },
+});

main.js

@@ -2,9 +2,9 @@
 
 import core from "@actions/core";
 import { createAppAuth } from "@octokit/auth-app";
-import { request } from "@octokit/request";
 
 import { main } from "./lib/main.js";
+import request from "./lib/request.js";
 
 if (!process.env.GITHUB_REPOSITORY) {
   throw new Error("GITHUB_REPOSITORY missing, must be set to '<owner>/<repo>'");

post.js

@@ -1,9 +1,9 @@
 // @ts-check
 
 import core from "@actions/core";
-import { request } from "@octokit/request";
 
 import { post } from "./lib/post.js";
+import request from "./lib/request.js";
 
 post(
   core,