Add Gitlab webhook installation documentation

INSTALL.md

@@ -343,6 +343,27 @@ PYTHONPATH="/PATH/TO/PROJECTS/pr-agent" python pr_agent/cli.py \
   review
 ```
 
+---
+
+### Method 8 - Run a GitLab webhook server
+
+1. From the GitLab workspace or group, create an access token. Enable the "api" scope only.
+2. Generate a random secret for your app, and save it for later. For example, you can use:
+
+```
+WEBHOOK_SECRET=$(python -c "import secrets; print(secrets.token_hex(10))")
+```
+3. Follow the instructions to build the Docker image, setup a secrets file and deploy on your own server from [Method 5](#method-5-run-as-a-github-app).
+4. In the secrets file, fill in the following:
+    - Your OpenAI key.
+    - In the [gitlab] section, fill in personal_access_token and shared_secret. The access token can be a personal access token, or a group or project access token.
+    - Set deployment_type to 'gitlab' in [configuration.toml](./pr_agent/settings/configuration.toml)
+5. Create a webhook in GitLab. Set the URL to the URL of your app's server. Set the secret token to the generated secret from step 2. 
+In the "Trigger" section, check the ‘comments’ and ‘merge request events’ boxes. 
+6. Test your installation by opening a merge request or commenting or a merge request using one of CodiumAI's commands.
+
+---
+
 ### Appendix - **Debugging LLM API Calls**  
 If you're testing your codium/pr-agent server, and need to see if calls were made successfully + the exact call logs, you can use the [LiteLLM Debugger tool](https://docs.litellm.ai/docs/debugging/hosted_debugging). 
 

README.md

@@ -154,6 +154,7 @@ There are several ways to use PR-Agent:
   - Allowing you to automate the review process on your private or public repositories
 - [Method 6: Deploy as a Lambda Function](INSTALL.md#method-6---deploy-as-a-lambda-function)
 - [Method 7: AWS CodeCommit](INSTALL.md#method-7---aws-codecommit-setup)
+- [Method 8: Run a GitLab webhook server](INSTALL.md#method-8---run-a-gitlab-webhook-server)
 
 ## How it works