Move context from modules to services (#29440)

Since `modules/context` has to depend on `models` and many other
packages, it should be moved from `modules/context` to
`services/context` according to design principles. There is no logic
code change on this PR, only move packages.

- Move `code.gitea.io/gitea/modules/context` to
`code.gitea.io/gitea/services/context`
- Move `code.gitea.io/gitea/modules/contexttest` to
`code.gitea.io/gitea/services/contexttest` because of depending on
context
- Move `code.gitea.io/gitea/modules/upload` to
`code.gitea.io/gitea/services/context/upload` because of depending on
context

services/context/context_model.go

@@ -0,0 +1,29 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package context
+
+import (
+	"code.gitea.io/gitea/models/unit"
+)
+
+// IsUserSiteAdmin returns true if current user is a site admin
+func (ctx *Context) IsUserSiteAdmin() bool {
+	return ctx.IsSigned && ctx.Doer.IsAdmin
+}
+
+// IsUserRepoAdmin returns true if current user is admin in current repo
+func (ctx *Context) IsUserRepoAdmin() bool {
+	return ctx.Repo.IsAdmin()
+}
+
+// IsUserRepoWriter returns true if current user has write privilege in current repo
+func (ctx *Context) IsUserRepoWriter(unitTypes []unit.Type) bool {
+	for _, unitType := range unitTypes {
+		if ctx.Repo.CanWrite(unitType) {
+			return true
+		}
+	}
+
+	return false
+}