feat: implement Nginx service with upstream management and configuration generation

apps/api/src/services/nginx/builder.rs

@@ -0,0 +1,47 @@
+use crate::services::nginx::info::upstream::UpstreamInfo;
+
+pub const INDENT_SIZE: usize = 2;
+
+pub trait NginxConfigProvider {
+    fn to_nginx_config(&self, indent: Option<usize>) -> String;
+}
+
+pub struct NginxConfigBuilder {
+    upstreams: Vec<UpstreamInfo>,
+}
+
+impl NginxConfigBuilder {
+    pub fn new() -> Self {
+        Self {
+            upstreams: Vec::new(),
+        }
+    }
+
+    pub fn add_upstream(&mut self, upstream: UpstreamInfo) {
+        self.upstreams.push(upstream);
+    }
+
+    pub fn add_upstreams(&mut self, upstreams: Vec<UpstreamInfo>) {
+        for upstream in upstreams {
+            self.add_upstream(upstream);
+        }
+    }
+}
+
+impl NginxConfigProvider for NginxConfigBuilder {
+    fn to_nginx_config(&self, indent: Option<usize>) -> String {
+        let mut config = format!(
+            "# Nginx Config Generated by YANPM at {}",
+            chrono::Utc::now()
+        );
+
+        for upstream in &self.upstreams {
+            config.push('\n');
+            config.push_str(&upstream.to_nginx_config(indent));
+        }
+
+        // TODO: Add other sections like servers, locations, etc.
+
+        config
+    }
+}