[GITEA] add option for banning dots in usernames

Refs: https://codeberg.org/forgejo/forgejo/pulls/676

Author:    Panagiotis "Ivory" Vasilopoulos <git@n0toose.net>
Date:      Mon Jun 12 13:57:01 2023 +0200

Co-authored-by: Gusted <postmaster@gusted.xyz>
(cherry picked from commit fabdda5c6e)
(cherry picked from commit d2c7f45621)
(cherry picked from commit dfdbaba3d6)
(cherry picked from commit a3cda092b8)
(cherry picked from commit f0fdb5905c)
(cherry picked from commit 9697e48c1f)
(cherry picked from commit 46e31009a8)
(cherry picked from commit 5bb2c54b6f)
(cherry picked from commit 682f9d24e1)
(cherry picked from commit 1863481005)
(cherry picked from commit 4f1b7c4ddb)
(cherry picked from commit 6afe70bbf1)
(cherry picked from commit 5cec1d9c2d)

Conflicts:
	templates/admin/config.tmpl
	https://codeberg.org/forgejo/forgejo/pulls/1512
(cherry picked from commit de2d172473)
(cherry picked from commit 37a3172dd9)

modules/validation/helpers_test.go

@@ -155,7 +155,8 @@ func Test_IsValidExternalTrackerURLFormat(t *testing.T) {
 	}
 }
 
-func TestIsValidUsername(t *testing.T) {
+func TestIsValidUsernameAllowDots(t *testing.T) {
+	setting.Service.AllowDotsInUsernames = true
 	tests := []struct {
 		arg  string
 		want bool
@@ -185,3 +186,31 @@ func TestIsValidUsername(t *testing.T) {
 		})
 	}
 }
+
+func TestIsValidUsernameBanDots(t *testing.T) {
+	setting.Service.AllowDotsInUsernames = false
+	defer func() {
+		setting.Service.AllowDotsInUsernames = true
+	}()
+
+	tests := []struct {
+		arg  string
+		want bool
+	}{
+		{arg: "a", want: true},
+		{arg: "abc", want: true},
+		{arg: "0.b-c", want: false},
+		{arg: "a.b-c_d", want: false},
+		{arg: ".abc", want: false},
+		{arg: "abc.", want: false},
+		{arg: "a..bc", want: false},
+		{arg: "a...bc", want: false},
+		{arg: "a.-bc", want: false},
+		{arg: "a._bc", want: false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.arg, func(t *testing.T) {
+			assert.Equalf(t, tt.want, IsValidUsername(tt.arg), "IsValidUsername[AllowDotsInUsernames=false](%v)", tt.arg)
+		})
+	}
+}