feat: support Gemini openai compatible api

relay/adaptor/geminiv2/main.go

@@ -0,0 +1,14 @@
+package geminiv2
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/songquanpeng/one-api/relay/meta"
+)
+
+func GetRequestURL(meta *meta.Meta) (string, error) {
+	baseURL := strings.TrimSuffix(meta.BaseURL, "/")
+	requestPath := strings.TrimPrefix(meta.RequestURLPath, "/v1")
+	return fmt.Sprintf("%s%s", baseURL, requestPath), nil
+}