Never use /api/v1 from Gitea UI Pages (#19318)

Reusing `/api/v1` from Gitea UI Pages have pros and cons.
Pros:
1) Less code copy

Cons:
1) API/v1 have to support shared session with page requests.
2) You need to consider for each other when you want to change something about api/v1 or page.

This PR moves all dependencies to API/v1 from UI Pages.

Partially replace #16052

modules/context/utils.go

@@ -0,0 +1,56 @@
+// Copyright 2017 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package context
+
+import (
+	"net/url"
+	"strings"
+	"time"
+)
+
+// GetQueryBeforeSince return parsed time (unix format) from URL query's before and since
+func GetQueryBeforeSince(ctx *Context) (before, since int64, err error) {
+	qCreatedBefore, err := prepareQueryArg(ctx, "before")
+	if err != nil {
+		return 0, 0, err
+	}
+
+	qCreatedSince, err := prepareQueryArg(ctx, "since")
+	if err != nil {
+		return 0, 0, err
+	}
+
+	before, err = parseTime(qCreatedBefore)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	since, err = parseTime(qCreatedSince)
+	if err != nil {
+		return 0, 0, err
+	}
+	return before, since, nil
+}
+
+// parseTime parse time and return unix timestamp
+func parseTime(value string) (int64, error) {
+	if len(value) != 0 {
+		t, err := time.Parse(time.RFC3339, value)
+		if err != nil {
+			return 0, err
+		}
+		if !t.IsZero() {
+			return t.Unix(), nil
+		}
+	}
+	return 0, nil
+}
+
+// prepareQueryArg unescape and trim a query arg
+func prepareQueryArg(ctx *Context, name string) (value string, err error) {
+	value, err = url.PathUnescape(ctx.FormString(name))
+	value = strings.TrimSpace(value)
+	return
+}