Refactor the setting to make unit test easier (#22405)

Some bugs caused by less unit tests in fundamental packages. This PR
refactor `setting` package so that create a unit test will be easier
than before.

- All `LoadFromXXX` files has been splited as two functions, one is
`InitProviderFromXXX` and `LoadCommonSettings`. The first functions will
only include the code to create or new a ini file. The second function
will load common settings.
- It also renames all functions in setting from `newXXXService` to
`loadXXXSetting` or `loadXXXFrom` to make the function name less
confusing.
- Move `XORMLog` to `SQLLog` because it's a better name for that.

Maybe we should finally move these `loadXXXSetting` into the `XXXInit`
function? Any idea?

---------

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: delvh <dev.lh@web.de>

modules/setting/api.go

@@ -0,0 +1,40 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"net/url"
+	"path"
+
+	"code.gitea.io/gitea/modules/log"
+)
+
+// API settings
+var API = struct {
+	EnableSwagger          bool
+	SwaggerURL             string
+	MaxResponseItems       int
+	DefaultPagingNum       int
+	DefaultGitTreesPerPage int
+	DefaultMaxBlobSize     int64
+}{
+	EnableSwagger:          true,
+	SwaggerURL:             "",
+	MaxResponseItems:       50,
+	DefaultPagingNum:       30,
+	DefaultGitTreesPerPage: 1000,
+	DefaultMaxBlobSize:     10485760,
+}
+
+func loadAPIFrom(rootCfg ConfigProvider) {
+	mustMapSetting(rootCfg, "api", &API)
+
+	defaultAppURL := string(Protocol) + "://" + Domain + ":" + HTTPPort
+	u, err := url.Parse(rootCfg.Section("server").Key("ROOT_URL").MustString(defaultAppURL))
+	if err != nil {
+		log.Fatal("Invalid ROOT_URL '%s': %s", AppURL, err)
+	}
+	u.Path = path.Join(u.Path, "api", "swagger")
+	API.SwaggerURL = u.String()
+}