Refactor hardcoded values and add comments

Author: hanelliotphan

dockerfile-image-update/src/main/java/com/salesforce/dockerfileimageupdate/utils/GithubAppCheck.java

@@ -64,13 +64,14 @@ public GithubAppCheck(final Namespace ns){
      * Method to verify whether the github app is installed on a repository or not. 
      * @param fullRepoName = The repository full name, i.e, of the format "owner/repoName". Eg: "Salesforce/dockerfile-image-update"
      * @return True if github app is installed, false otherwise. 
+     * Reference: https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/generating-a-json-web-token-jwt-for-a-github-app
      */
     protected boolean isGithubAppEnabledOnRepository(String fullRepoName) {
         refreshJwtIfNeeded(appId, privateKeyPath);
         try {
-            // Return true if the app is found on the repository via JWT token and API call
-            // Reference: https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/generating-a-json-web-token-jwt-for-a-github-app
-            gitHub.getApp().getInstallationByRepository(fullRepoName.split("/")[0], fullRepoName.split("/")[1]);
+            String org = fullRepoName.split("/")[0];
+            String repo = fullRepoName.split("/")[1];
+            gitHub.getApp().getInstallationByRepository(org, repo);
             return true;
         } catch (HttpException exception) {
             if (exception.getResponseCode() != 404) {
@@ -93,7 +94,6 @@ protected boolean isGithubAppEnabledOnRepository(String fullRepoName) {
     private void refreshJwtIfNeeded(String appId, String privateKeyPath) {
         if (jwt == null || jwtExpiry.isBefore(Instant.now().minusSeconds(jwtRefreshBuffer))) {  // Adding a buffer to ensure token validity
             try {
-                // Generate JWT token 60 seconds before the expiry to continue Github app check
                 generateJWT(appId, privateKeyPath);
             } catch (IOException | GeneralSecurityException exception) {
                 log.warn("Could not refresh the JWT due to exception: {}", exception.getMessage());