repo: milestone: make /milestone/:id endpoint accessible (#11264) (#11282)

Previously, this required authentication, but there's not actually
any privileged information on this page.  Move the endpoint out of
the group that requires sign-in.  It still requires the ability to
read issues and pull requests, so private repositories (for instance)
will not be exposed.

Fixes #10312 
Fixes #11233

Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>

routers/routes/routes.go

@@ -668,6 +668,14 @@ func RegisterRoutes(m *macaron.Macaron) {
 
 	m.Post("/:username/:reponame/action/:action", reqSignIn, context.RepoAssignment(), context.UnitTypes(), repo.Action)
 
+	// Grouping for those endpoints not requiring authentication
+	m.Group("/:username/:reponame", func() {
+		m.Group("/milestone", func() {
+			m.Get("/:id", repo.MilestoneIssuesAndPulls)
+		}, reqRepoIssuesOrPullsReader, context.RepoRef())
+	}, context.RepoAssignment(), context.UnitTypes())
+
+	// Grouping for those endpoints that do require authentication
 	m.Group("/:username/:reponame", func() {
 		m.Group("/issues", func() {
 			m.Combo("/new").Get(context.RepoRef(), repo.NewIssue).
@@ -723,9 +731,6 @@ func RegisterRoutes(m *macaron.Macaron) {
 			m.Post("/:id/:action", repo.ChangeMilestonStatus)
 			m.Post("/delete", repo.DeleteMilestone)
 		}, context.RepoMustNotBeArchived(), reqRepoIssuesOrPullsWriter, context.RepoRef())
-		m.Group("/milestone", func() {
-			m.Get("/:id", repo.MilestoneIssuesAndPulls)
-		}, reqRepoIssuesOrPullsReader, context.RepoRef())
 		m.Combo("/compare/*", repo.MustBeNotEmpty, reqRepoCodeReader, repo.SetEditorconfigIfExists).
 			Get(repo.SetDiffViewStyle, repo.CompareDiff).
 			Post(context.RepoMustNotBeArchived(), reqRepoPullsReader, repo.MustAllowPulls, bindIgnErr(auth.CreateIssueForm{}), repo.CompareAndPullRequestPost)