Add ContextUser to http request context (#18798)

This PR adds a middleware which sets a ContextUser (like GetUserByParams before) in a single place which can be used by other methods. For routes which represent a repo or org the respective middlewares set the field too.

Also fix a bug in modules/context/org.go during refactoring.

services/context/user.go

@@ -0,0 +1,62 @@
+// Copyright 2022 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 (
+	"fmt"
+	"net/http"
+	"strings"
+
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/context"
+)
+
+// UserAssignmentWeb returns a middleware to handle context-user assignment for web routes
+func UserAssignmentWeb() func(ctx *context.Context) {
+	return func(ctx *context.Context) {
+		userAssignment(ctx, func(status int, title string, obj interface{}) {
+			err, ok := obj.(error)
+			if !ok {
+				err = fmt.Errorf("%s", obj)
+			}
+			if status == http.StatusNotFound {
+				ctx.NotFound(title, err)
+			} else {
+				ctx.ServerError(title, err)
+			}
+		})
+	}
+}
+
+// UserAssignmentAPI returns a middleware to handle context-user assignment for api routes
+func UserAssignmentAPI() func(ctx *context.APIContext) {
+	return func(ctx *context.APIContext) {
+		userAssignment(ctx.Context, ctx.Error)
+	}
+}
+
+func userAssignment(ctx *context.Context, errCb func(int, string, interface{})) {
+	username := ctx.Params(":username")
+
+	if ctx.IsSigned && ctx.Doer.LowerName == strings.ToLower(username) {
+		ctx.ContextUser = ctx.Doer
+	} else {
+		var err error
+		ctx.ContextUser, err = user_model.GetUserByName(username)
+		if err != nil {
+			if user_model.IsErrUserNotExist(err) {
+				if redirectUserID, err := user_model.LookupUserRedirect(username); err == nil {
+					context.RedirectToUser(ctx, username, redirectUserID)
+				} else if user_model.IsErrUserRedirectNotExist(err) {
+					errCb(http.StatusNotFound, "GetUserByName", err)
+				} else {
+					errCb(http.StatusInternalServerError, "LookupUserRedirect", err)
+				}
+			} else {
+				errCb(http.StatusInternalServerError, "GetUserByName", err)
+			}
+		}
+	}
+}