feat: able to change gemini safety setting (#867)

* perf: adjust gemini safety settings, set BLOCK_NONE by default

* feat: able to adjust by env variable

---------

Co-authored-by: JustSong <songquanpeng@foxmail.com>

common/utils.go

@@ -196,6 +196,13 @@ func GetOrDefault(env string, defaultValue int) int {
 	return num
 }
 
+func GetOrDefaultString(env string, defaultValue string) string {
+	if env == "" || os.Getenv(env) == "" {
+		return defaultValue
+	}
+	return os.Getenv(env)
+}
+
 func MessageWithRequestId(message string, id string) string {
 	return fmt.Sprintf("%s (request id: %s)", message, id)
 }