feat: Implement SSH Agent Connector and gRPC server

- Added `AgentConnectorTrait` and `AgentConnector` for managing agent connections.
- Introduced `SshAgentConnector` to handle SSH-related functionalities and start a gRPC server.
- Created database entities for `agents`, `certificates`, `organizations`, `public_key_revocations`, `setup_tokens`, `upstreams`, `users`, `virtual_hosts`, and `workspaces` using SeaORM.
- Developed `CertificateService` for managing certificate generation and retrieval.
- Implemented the main server logic to initialize the database connection and start the agent server.
- Configured development settings in `development.toml` for server and database connections.

apps/nxmesh-master/src/main.rs

@@ -0,0 +1,84 @@
+#![forbid(unsafe_code, unused_must_use)]
+#![deny(clippy::unwrap_used, clippy::panic, clippy::expect_used)]
+
+use clap::{CommandFactory, Parser};
+use tracing::{error, info};
+use tracing_subscriber::{
+    Layer, filter::LevelFilter, fmt, layer::SubscriberExt, registry::Registry, reload,
+    util::SubscriberInitExt,
+};
+
+use crate::cli::{Cli, handle_sub_command};
+
+mod cli;
+mod config;
+mod connector;
+mod db;
+mod service;
+
+#[tokio::main]
+async fn main() {
+    // install a global subscriber for logging
+    let reload_handle = install_tracing_subscriber();
+    // Load configuration settings
+    let settings = match config::settings::Settings::load() {
+        Ok(s) => s,
+        Err(e) => {
+            error!("Failed to load configuration: {}", e);
+            std::process::exit(1);
+        }
+    };
+
+    reload_handle
+        .modify(|filter| *filter = Box::new(settings.log.level))
+        .inspect_err(|e| {
+            error!(
+                "Failed to set log level: {}. Continuing with default level.",
+                e
+            )
+        })
+        // ignore errors here since we can still run with the default log level
+        .ok();
+
+    // print the loaded settings for debugging
+    // info!("Loaded settings: {:#?}", settings);
+    let cli = Cli::parse();
+
+    if cli.serve {
+        info!("Starting master server...");
+        if let Err(e) = service::start_master_server(settings, cli).await {
+            error!("Failed to start master server: {}", e);
+            std::process::exit(1);
+        }
+    } else if let Some(command) = cli.command {
+        handle_sub_command(&settings, command)
+            .await
+            .unwrap_or_else(|e| {
+                error!("Error handling command: {}", e);
+                std::process::exit(1);
+            });
+    } else {
+        error!("No mode specified.");
+        // display help message
+        #[allow(clippy::expect_used)]
+        Cli::command()
+            .print_help()
+            .expect("Failed to print help message");
+        std::process::exit(1);
+    }
+}
+
+fn install_tracing_subscriber()
+-> reload::Handle<Box<dyn tracing_subscriber::layer::Layer<Registry> + Send + Sync>, Registry> {
+    let filter = LevelFilter::INFO;
+    let (filter_layer, reload_handle) =
+        reload::Layer::new(Box::new(fmt::layer().with_filter(filter))
+            as Box<dyn tracing_subscriber::layer::Layer<Registry> + Send + Sync>);
+
+    tracing_subscriber::registry()
+        .with(filter_layer)
+        .with(fmt::Layer::default())
+        .init();
+
+    reload_handle
+}