[MM-12958] Support running two Mattermost instances on the same domain using subpaths (#10493)

app/oauth.go

@@ -654,11 +654,13 @@ func (a *App) GetAuthorizationCode(w http.ResponseWriter, r *http.Request, servi
 	}
 
 	cookieValue := model.NewId()
+	subpath, _ := utils.GetSubpathFromConfig(a.Config())
+
 	expiresAt := time.Unix(model.GetMillis()/1000+int64(OAUTH_COOKIE_MAX_AGE_SECONDS), 0)
 	oauthCookie := &http.Cookie{
 		Name:     COOKIE_OAUTH,
 		Value:    cookieValue,
-		Path:     "/",
+		Path:     subpath,
 		MaxAge:   OAUTH_COOKIE_MAX_AGE_SECONDS,
 		Expires:  expiresAt,
 		HttpOnly: true,
@@ -741,10 +743,12 @@ func (a *App) AuthorizeOAuthUser(w http.ResponseWriter, r *http.Request, service
 		mlog.Error(appErr.Error())
 	}
 
+	subpath, _ := utils.GetSubpathFromConfig(a.Config())
+
 	httpCookie := &http.Cookie{
 		Name:     COOKIE_OAUTH,
 		Value:    "",
-		Path:     "/",
+		Path:     subpath,
 		MaxAge:   -1,
 		HttpOnly: true,
 	}