PLT-5900 Removed automatic configuration of SiteURL (#5952)

* Revert "PLT-5765 Passed SiteURL to SendNotifications (#5705)"

This reverts commit a8e68bd890.

* Removed automatic configuration of SiteURL

* Reverted unintentional config changes

* Updated help text

* Added link to docs in Site URL warning

* Fixed merge conflict

api4/context.go

@@ -19,14 +19,14 @@ import (
 )
 
 type Context struct {
-	Session   model.Session
-	Params    *ApiParams
-	Err       *model.AppError
-	T         goi18n.TranslateFunc
-	RequestId string
-	IpAddress string
-	Path      string
-	siteURL   string
+	Session       model.Session
+	Params        *ApiParams
+	Err           *model.AppError
+	T             goi18n.TranslateFunc
+	RequestId     string
+	IpAddress     string
+	Path          string
+	siteURLHeader string
 }
 
 func ApiHandler(h func(*Context, http.ResponseWriter, *http.Request)) http.Handler {
@@ -125,12 +125,7 @@ func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		isTokenFromQueryString = true
 	}
 
-	if utils.GetSiteURL() == "" {
-		protocol := app.GetProtocol(r)
-		c.SetSiteURL(protocol + "://" + r.Host)
-	} else {
-		c.SetSiteURL(utils.GetSiteURL())
-	}
+	c.SetSiteURLHeader(app.GetProtocol(r) + "://" + r.Host)
 
 	w.Header().Set(model.HEADER_REQUEST_ID, c.RequestId)
 	w.Header().Set(model.HEADER_VERSION_ID, fmt.Sprintf("%v.%v.%v.%v", model.CurrentVersion, model.BuildNumber, utils.CfgHash, utils.IsLicensed))
@@ -320,12 +315,12 @@ func (c *Context) SetPermissionError(permission *model.Permission) {
 	c.Err.StatusCode = http.StatusForbidden
 }
 
-func (c *Context) SetSiteURL(url string) {
-	c.siteURL = strings.TrimRight(url, "/")
+func (c *Context) SetSiteURLHeader(url string) {
+	c.siteURLHeader = strings.TrimRight(url, "/")
 }
 
-func (c *Context) GetSiteURL() string {
-	return c.siteURL
+func (c *Context) GetSiteURLHeader() string {
+	return c.siteURLHeader
 }
 
 func (c *Context) RequireUserId() *Context {