Add test connection feature for database targets

This commit introduces a new endpoint to test database connection. The frontend now includes a button to test the connection before creating a target, with real-time feedback on success or failure. Related styles and components were updated for better user experience.

backend/app/api/routes/targets.py

@@ -8,7 +8,7 @@ from app.core.deps import get_current_user, require_roles
 from app.models.models import Metric, QueryStat, Target, User
 from app.schemas.metric import MetricOut, QueryStatOut
 from app.schemas.overview import DatabaseOverviewOut
-from app.schemas.target import TargetCreate, TargetOut, TargetUpdate
+from app.schemas.target import TargetConnectionTestRequest, TargetCreate, TargetOut, TargetUpdate
 from app.services.audit import write_audit_log
 from app.services.collector import build_target_dsn
 from app.services.crypto import encrypt_secret
@@ -23,6 +23,33 @@ async def list_targets(user: User = Depends(get_current_user), db: AsyncSession
     return [TargetOut.model_validate(item) for item in targets]
 
 
+@router.post("/test-connection")
+async def test_target_connection(
+    payload: TargetConnectionTestRequest,
+    user: User = Depends(require_roles("admin", "operator")),
+) -> dict:
+    _ = user
+    ssl = False if payload.sslmode == "disable" else True
+    conn = None
+    try:
+        conn = await asyncpg.connect(
+            host=payload.host,
+            port=payload.port,
+            database=payload.dbname,
+            user=payload.username,
+            password=payload.password,
+            ssl=ssl,
+            timeout=8,
+        )
+        version = await conn.fetchval("SHOW server_version")
+        return {"ok": True, "message": "Connection successful", "server_version": version}
+    except Exception as exc:
+        raise HTTPException(status_code=400, detail=f"Connection failed: {exc}")
+    finally:
+        if conn:
+            await conn.close()
+
+
 @router.post("", response_model=TargetOut, status_code=status.HTTP_201_CREATED)
 async def create_target(
     payload: TargetCreate,

backend/app/schemas/target.py

@@ -16,6 +16,15 @@ class TargetCreate(TargetBase):
     password: str
 
 
+class TargetConnectionTestRequest(BaseModel):
+    host: str
+    port: int = 5432
+    dbname: str
+    username: str
+    password: str
+    sslmode: str = "prefer"
+
+
 class TargetUpdate(BaseModel):
     name: str | None = None
     host: str | None = None