SQL preflight connection validation (#4150)

* wip sql connection string validation

* handle failed sql connections in frontend

* sql preflight connection validation on modal save

* revert unneeded be/fe changes

* linting, form updates

---------

Co-authored-by: timothycarambat <rambat1010@gmail.com>

server/utils/agents/aibitat/plugins/sql-agent/SQLConnectors/Postgresql.js

@@ -22,7 +22,7 @@ class PostgresSQLConnector {
   /**
    *
    * @param {string} queryString the SQL query to be run
-   * @returns {import(".").QueryResult}
+   * @returns {Promise<import(".").QueryResult>}
    */
   async runQuery(queryString = "") {
     const result = { rows: [], count: 0, error: null };
@@ -35,12 +35,24 @@ class PostgresSQLConnector {
       console.log(this.constructor.name, err);
       result.error = err.message;
     } finally {
-      await this._client.end();
-      this.#connected = false;
+      // Check client is connected before closing since we use this for validation
+      if (this._client) {
+        await this._client.end();
+        this.#connected = false;
+      }
     }
     return result;
   }
 
+  async validateConnection() {
+    try {
+      const result = await this.runQuery("SELECT 1");
+      return { success: !result.error, error: result.error };
+    } catch (error) {
+      return { success: false, error: error.message };
+    }
+  }
+
   getTablesSql() {
     return `SELECT * FROM pg_catalog.pg_tables WHERE schemaname = 'public'`;
   }