NGX-860: Custom NGINX Server Includes (#67)

* NGX-860: Custom NGINX Server Includes

- Add a line to the template to include customer user includes within /etc/nginx/user-includes.d/
- Add block comments to various location blocks in NGINX config to inform the user of each block's purpose

* NGX-860: Remove extra newline

templates/etc/nginx/conf.d/site.conf.j2

@@ -78,6 +78,13 @@ server {
         set $cache_bypass 1;
     }
 
+    # Default Request Handling: This block is the catch-all for any requests not matched by other location
+    # blocks. It forwards requests to an Apache backend, preserving important request headers to ensure
+    # accurate IP, protocol, and host information is passed along. Caching directives are applied
+    # conditionally, based on the 'cache_bypass' variable, allowing certain requests to bypass the cache
+    # for fresh content retrieval or to avoid caching altogether. The 'X-Proxy-Cache' header provides
+    # visibility into the cache status of responses. This setup ensures that the backend handles most
+    # dynamic content, while still allowing for flexible cache control to optimize performance.
     location / {
         add_header X-Proxy-Cache $upstream_cache_status;
 
@@ -102,6 +109,14 @@ server {
     }
 
 {% if nginx_accel_static_content %}
+    # Static File Caching: This location block applies caching policies to a variety of static file types
+    # commonly served by web applications, including images, executable files, compressed archives,
+    # documents, stylesheets, scripts, fonts, and media files. The 'expires' directive sets a cache
+    # duration of 7 days, and the 'Cache-Control' header is configured to make these resources publicly
+    # cacheable while still requiring revalidation. Additionally, a custom 'X-Proxy-Cache' header marks
+    # these responses for easy identification as static resources in proxy caching mechanisms. This
+    # approach enhances client-side caching, reducing load times for repeat visitors and decreasing
+    # server load by encouraging browsers to cache these resources.
     location ~* \.(ico|jpe?g|gif|png|bmp|svg|tiff|exe|dmg|zip|rar|7z|docx?|xlsx?|js|css|less|sass|scss|ttf|woff2?|mp3|mp4|mkv|avi|mov|mpe?g|aac|wav|flac)$ {
         expires 7d;
         add_header Cache-Control "public, must-revalidate";
@@ -110,6 +125,11 @@ server {
 {% endif %}
 
 {% if nginx_ratelimit_enable %}
+    # Rate Limiting for WordPress Core Files: Targets critical WordPress PHP files such as login,
+    # XML-RPC, and WP-Cron to apply rate limiting and prevent abuse (e.g., brute force attacks,
+    # spamming). The limit_req directive is configured to respond with a 429 status code if requests
+    # exceed the defined rate, allowing bursts of up to 10 requests. Caching for these requests is
+    # explicitly disabled to ensure live processing and security.
     location ~ {{ nginx_ratelimit_paths }} {
         limit_req_status 429;
         limit_req zone={{ nginx_ratelimit_zone }} burst={{ nginx_ratelimit_burst }}{% if nginx_ratelimit_nodelay %} nodelay{% endif %};
@@ -133,6 +153,11 @@ server {
     }
 {% endif %}
 
+    # Dynamic Content Handling: This location block matches URLs for user-specific pages,
+    # administrative areas, and sensitive PHP scripts (e.g., opcache, phpinfo) where caching
+    # is not desirable to ensure fresh content delivery and security. It bypasses cache and
+    # prevents caching of these responses. Adjust patterns as necessary to match your
+    # application's URL structure for dynamic content.
     location ~ "{{ nginx_cache_bypass_paths }}" {
         proxy_no_cache 1;
         proxy_cache_bypass 1;
@@ -152,13 +177,21 @@ server {
     }
 
 {% if nginx_cache_purge_enable %}
+    # Cache Purging Endpoint: This location block is designed to handle cache purging requests.
+    # Only requests from the server's IP (127.0.0.1) and the server IP are allowed.
+    # The 'proxy_cache_purge' directive clears cached content for the specified URL pattern.
     location ~ ^/purge(/.*) {
         allow 127.0.0.1;
         allow {{ ansible_default_ipv4.address }};
         deny all;
         proxy_cache_purge sitecache "$scheme$request_method$host$1";
     }
 {% endif %}
+
+    # Include custom server configurations provided by users.
+    # This allows for flexible customization while maintaining core server settings.
+    include /etc/nginx/user-includes.d/*.conf;
+
 {% if site_domain == ansible_nodename and goaccess_enabled is defined and goaccess_enabled | bool %}
     location /goaccess {
         root /usr/share/nginx/html;