Update documentation for connector-service endpoint

Updated design and feature flag documentation to reflect new endpoint:
- DESIGN.md: Updated code example to use connector-service endpoint
- ADDING_FEATURE_FLAGS.md: Updated API documentation and response format

The documentation now correctly shows:
- Endpoint: /api/2.0/connector-service/feature-flags/GOLANG/{version}
- Response format with array of flag entries
- Removed outdated query parameter references

Signed-off-by: Samikshya Chand <samikshya.chand@databricks.com>
Signed-off-by: samikshya-chand_data <samikshya.chand@databricks.com>

Author: samikshya-db

telemetry/ADDING_FEATURE_FLAGS.md

@@ -62,10 +62,21 @@ if enabled {
 
 ## How It Works
 
-### Single Request for All Flags
-All flags are fetched together in a single HTTP request:
+### Connector Service Endpoint
+Flags are fetched from the connector-service endpoint with driver name and version:
 ```
-GET /api/2.0/feature-flags?flags=flagOne,flagTwo,flagThree
+GET /api/2.0/connector-service/feature-flags/GOLANG/{driverVersion}
+```
+
+The response includes all available flags for the driver:
+```json
+{
+  "flags": [
+    {"name": "flagOne", "value": "true"},
+    {"name": "flagTwo", "value": "false"}
+  ],
+  "ttl_seconds": 900
+}
 ```
 
 ### 15-Minute Cache

telemetry/DESIGN.md

@@ -1531,19 +1531,15 @@ func ParseTelemetryConfig(params map[string]string) *Config {
 
 ```go
 // checkFeatureFlag checks if telemetry is enabled server-side.
-func checkFeatureFlag(ctx context.Context, host string, httpClient *http.Client) (bool, error) {
-	endpoint := fmt.Sprintf("https://%s/api/2.0/feature-flags", host)
+func checkFeatureFlag(ctx context.Context, host string, httpClient *http.Client, driverVersion string) (bool, error) {
+	// Use connector-service endpoint with driver name and version
+	endpoint := fmt.Sprintf("https://%s/api/2.0/connector-service/feature-flags/GOLANG/%s", host, driverVersion)
 
 	req, err := http.NewRequestWithContext(ctx, "GET", endpoint, nil)
 	if err != nil {
 		return false, err
 	}
 
-	// Add query parameters
-	q := req.URL.Query()
-	q.Add("flags", "databricks.partnerplatform.clientConfigsFeatureFlags.enableTelemetryForGoDriver")
-	req.URL.RawQuery = q.Encode()
-
 	resp, err := httpClient.Do(req)
 	if err != nil {
 		return false, err