Update GitLab configuration and documentation for webhook setup

Usage.md

@@ -6,6 +6,7 @@
 - [Online Usage](#online-usage)
 - [GitHub App](#working-with-github-app)
 - [GitHub Action](#working-with-github-action)
+- [GitLab Webhook](#working-with-gitlab-webhook)
 - [BitBucket App](#working-with-bitbucket-self-hosted-app)
 - [Azure DevOps Provider](#azure-devops-provider)
 - [Additional Configurations Walkthrough](#appendix---additional-configurations-walkthrough)
@@ -237,6 +238,16 @@ For example, you can set an environment variable: `pr_description.add_original_u
 [pr_description]
 add_original_user_description = false
 ```
+### Working with GitLab Webhook
+After setting up a GitLab webhook, to control which commands will run automatically when a new PR is opened, you can set the `pr_commands` parameter in the configuration file, similar to the GitHub App:
+```
+[gitlab]
+pr_commands = [
+    "/describe --pr_description.add_original_user_description=true --pr_description.keep_original_user_title=true",
+    "/review --pr_reviewer.num_code_suggestions=0",
+    "/improve",
+]
+```
 
 ### Working with BitBucket Self-Hosted App
 Similar to GitHub app, when running PR-Agent from BitBucket App, the default [configuration file](pr_agent/settings/configuration.toml) from a pre-built docker will be initially loaded.

pr_agent/servers/gitlab_webhook.py

@@ -32,7 +32,7 @@ def handle_request(background_tasks: BackgroundTasks, url: str, body: str, log_c
 
 async def _perform_commands_gitlab(commands_conf: str, agent: PRAgent, body: dict, api_url: str, log_context: dict):
     apply_repo_settings(api_url)
-    commands = get_settings().get(f"azure_devops_server.{commands_conf}")
+    commands = get_settings().get(f"gitlab.{commands_conf}")
     for command in commands:
         split_command = command.split(" ")
         command = split_command[0]

pr_agent/settings/configuration.toml

@@ -171,17 +171,12 @@ push_commands = [
 ]
 
 [gitlab]
-# URL to the gitlab service
-url = "https://gitlab.com"
-
-# Polling (either project id or namespace/project_name) syntax can be used
-projects_to_monitor = ['org_name/repo_name']
-
-# Polling trigger
-magic_word = "AutoReview"
-
-# Polling interval
-polling_interval_seconds = 30
+url = "https://gitlab.com" # URL to the gitlab service
+pr_commands = [
+    "/describe --pr_description.add_original_user_description=true --pr_description.keep_original_user_title=true",
+    "/review --pr_reviewer.num_code_suggestions=0",
+    "/improve --pr_code_suggestions.summarize=true",
+]
 
 [bitbucket_app]
 #auto_review = true    # set as config var in .pr_agent.toml