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/cli/mod.rs

@@ -0,0 +1,63 @@
+mod gen_agent_certs;
+mod gen_certs;
+
+use clap::{Parser, Subcommand};
+
+use crate::{
+    cli::{gen_agent_certs::gen_agent_certs, gen_certs::gen_certs},
+    config::settings::Settings,
+};
+
+#[derive(Parser)]
+#[command(version, about, long_about = None)]
+pub struct Cli {
+    /// Start the master server
+    #[arg(short, long, group = "mode")]
+    pub serve: bool,
+
+    /// generate CA for key signing if not exist
+    /// If the CA already exists, generating CA will be skipped and the existing CA will be used
+    /// If the CA does not exist, a new CA will be generated and saved to the default location (./certs/ca.crt and ./certs/ca.key)
+    /// The generated CA will be used for signing agent certificates
+    /// If not specified, the server will check if the CA already exists and use it if available, otherwise exit with an error
+    #[arg(long)]
+    pub generate_ca: bool,
+
+    #[command(subcommand)]
+    pub command: Option<Commands>,
+}
+
+#[derive(Subcommand)]
+pub enum Commands {
+    GenCerts {
+        /// Output directory for generated certificates
+        #[arg(short, long, default_value = "./certs")]
+        output: String,
+    },
+    /// Generate certificates for agent
+    #[command(about = "Generate certificates for agent")]
+    GenAgentCerts {
+        /// Output directory for generated certificates
+        #[arg(short, long, default_value = "./certs")]
+        output: String,
+        #[arg(long, default_value = "agent-id-placeholder")]
+        agent_id: String,
+        #[arg(short, long, default_value = "false")]
+        zip: bool,
+    },
+}
+
+pub async fn handle_sub_command(
+    settings: &Settings,
+    command: Commands,
+) -> Result<(), Box<dyn std::error::Error>> {
+    // run as a CLI tool for other commands
+    match command {
+        Commands::GenCerts { output } => Ok(gen_certs(settings, output).await?),
+        Commands::GenAgentCerts {
+            output,
+            agent_id,
+            zip,
+        } => Ok(gen_agent_certs(settings, output, agent_id, zip).await?),
+    }
+}