Show links to access generated code easily in PR (#76)

In the `Show diff` step, all jobs display the differences of the
generated code. While some members have navigated by opening the GitHub
Actions job URL, it should be more convenient to comment directly on the
PR.

This change supports that.

(Additional Notes on the Comments)
1. Since the generated code may be updated with each additional commit,
the job deletes old comments containing old job URLs if present.
2. Some generators are incomplete, so the comment shows tasks directed
to the person who updated the OpenAPI YAML, especially when
`webhook.yml` is updated.

Author: Yang-33

.github/actions/post-comment-action/action.yml

@@ -0,0 +1,29 @@
+name: 'Post and Manage PR Comments'
+description: 'Posts comments to PR and deletes previous ones for the same job'
+inputs:
+  language:
+    description: 'The language of the SDK'
+    required: true
+  github-token:
+    description: 'The GitHub token'
+    required: true
+
+outputs: {}
+
+runs:
+  using: 'composite'
+  steps:
+    - name: check current directory
+      run: pwd
+      shell: bash
+    - name: Install dependencies
+      run: npm ci
+      shell: bash
+      working-directory: ${{ github.action_path }}
+
+    - name: Post PR comment
+      run: node ${{ github.action_path }}/main.js
+      shell: bash
+      env:
+        LANGUAGE: ${{ inputs.language }}
+        GITHUB_TOKEN: ${{ inputs.github-token }}

.github/actions/post-comment-action/main.js

@@ -0,0 +1,96 @@
+const github = require('@actions/github');
+const core = require('@actions/core');
+
+async function run() {
+    try {
+        const token = process.env.GITHUB_TOKEN;
+        const language = process.env.LANGUAGE;
+
+        const octokit = github.getOctokit(token);
+        const context = github.context;
+
+        const stepName = 'Show diff'
+
+        const prNumber = context.payload.pull_request.number;
+        const runId = context.runId;
+        const jobName = context.job;
+
+        // Delete the previous comment if it exists
+        const { data: comments } = await octokit.rest.issues.listComments({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            issue_number: prNumber,
+        });
+
+        const medadataForComment = `<!-- ${jobName}-comment -->`;
+
+        for (const comment of comments) {
+            if (
+                comment.user.login === 'github-actions[bot]' &&
+                comment.body.includes(medadataForComment)
+            ) {
+                await octokit.rest.issues.deleteComment({
+                    owner: context.repo.owner,
+                    repo: context.repo.repo,
+                    comment_id: comment.id,
+                });
+            }
+        }
+
+        // Post the new comment
+        const { data: { jobs } } = await octokit.rest.actions.listJobsForWorkflowRun({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            run_id: runId,
+        });
+
+        const currentJob = jobs.find(job => job.name === jobName);
+        if (!currentJob) {
+            throw new Error(`Job ${jobName} not found`);
+        }
+
+        const jobId = currentJob.id;
+
+        const step = currentJob.steps.find(step => step.name === stepName);
+        if (!step) {
+            throw new Error(`Step '${stepName}' not found`);
+        }
+
+        const stepNumber = currentJob.steps.indexOf(step) + 1;
+
+        const url = `https://github.com/${context.repo.owner}/${context.repo.repo}/actions/runs/${runId}/job/${jobId}?pr=${prNumber}#step:${stepNumber}:1`;
+
+        // Create comment as markdown
+        let fullCommentBody = `## ${language.toUpperCase()} \n` +
+            `You can check generated code in ${language}\n\n` +
+            `[Check the diff here](${url})`;
+
+        // for warning
+        if (language === 'ruby' || language === 'php') {
+            const { data: files } = await octokit.rest.pulls.listFiles({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                pull_number: prNumber,
+            });
+
+            const isWebhookEventAdded = files.some(file => file.filename.includes('webhook.yml'));
+            if (isWebhookEventAdded) {
+                fullCommentBody += "\n\n⚠️You may need to modify code when a webhook event is added, even when tests are passed." +
+                    `Parser in line-bot-sdk-${language} in not generated automatically.` +
+                    "Please add tests and modify parser manually in each repository before release.";
+            }
+        }
+
+        await octokit.rest.issues.createComment({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            issue_number: prNumber,
+            body: `${medadataForComment}\n${fullCommentBody}`,
+        });
+    } catch (error) {
+        console.error(error);
+        core.setFailed(`Error in this script: ${error.message}`);
+    }
+}
+
+run();