add GetQueryParam and GetURLParam functions

These functions retrieve the parameters and try to unescape
the values.

Author: weeco

rest/query_param.go

@@ -0,0 +1,32 @@
+// Copyright 2023 Redpanda Data, Inc.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.md
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0
+
+package rest
+
+import (
+	"net/http"
+	"net/url"
+)
+
+// GetQueryParam retrieves the query parameter with your given key from the request,
+// unescapes the value and returns it. If the query parameter does not exist an
+// empty string will be returned. If the unescaping fails the unescaped string
+// will be returned.
+func GetQueryParam(r *http.Request, key string) string {
+	val := r.URL.Query().Get(key)
+	if val == "" {
+		return ""
+	}
+
+	unescapedVal, err := url.QueryUnescape(val)
+	if err != nil {
+		return val
+	}
+	return unescapedVal
+}

rest/url_param.go

@@ -0,0 +1,34 @@
+// Copyright 2023 Redpanda Data, Inc.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.md
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0
+
+package rest
+
+import (
+	"net/http"
+	"net/url"
+
+	"github.com/go-chi/chi/v5"
+)
+
+// GetURLParam retrieves the url parameter with your given key from the request,
+// unescapes the value and returns it. If the url parameter does not exist an
+// empty string will be returned. If the unescaping fails the unescaped string
+// will be returned.
+func GetURLParam(r *http.Request, key string) string {
+	val := chi.URLParam(r, key)
+	if val == "" {
+		return ""
+	}
+
+	unescapedVal, err := url.PathUnescape(val)
+	if err != nil {
+		return val
+	}
+	return unescapedVal
+}