Add users option to both GitHub and Gitea restricting project owners

[MagicRB]

Hopefully closes #393

[MagicRB]

@zowoq this looks good? I tested the Gitea backend at it works, didn't test the GitHub one as I don't have GitHub setup, but it should work. @Mic92 can you test?

[zowoq]

Tested removing the topic and using only the repoAllowlist in nix-community, adding/removing repos works, did need to change the buildbot-nix topic default from build-with-buildbot to null.

-      topic = "nix-community-buildbot";
+      repoAllowlist = [
+        "nix-community/authentik-nix"
+        "nix-community/autofirma-nix"
+        "nix-community/dream2nix"
+        "nix-community/ethereum.nix"
+        "nix-community/infra"
+        "nix-community/lanzaboote"
+        "nix-community/neovim-nightly-overlay"
+        "nix-community/nix-direnv"
+        "nix-community/nix-index"
+        "nix-community/nix4nvchad"
+        "nix-community/NixNG"
+        "nix-community/nixos-facter"
+        "nix-community/nixos-facter-modules"
+        "nix-community/nixos-generators"
+        "nix-community/nixos-images"
+        "nix-community/nixpkgs-update"
+        "nix-community/nixpkgs-xr"
+        "nix-community/nixvim"
+        "nix-community/raspberry-pi-nix"
+        "nix-community/srvos"
+      ];

diff --git a/nix/master.nix b/nix/master.nix
index 2a75c8f74..3a3fc8854 100644
--- a/nix/master.nix
+++ b/nix/master.nix
@@ -374,7 +374,7 @@ in
         };
         topic = lib.mkOption {
           type = lib.types.nullOr lib.types.str;
-          default = "build-with-buildbot";
+          default = null;
           description = ''
             Projects that have this topic will be built by buildbot.
             If null, all projects that the buildbot Gitea user has access to, are built.
@@ -453,7 +453,7 @@ in
         };
         topic = lib.mkOption {
           type = lib.types.nullOr lib.types.str;
-          default = "build-with-buildbot";
+          default = null;
           description = ''
             Projects that have this topic will be built by buildbot.
             If null, all projects that the buildbot github user has access to, are built.

[MagicRB]

You should be able to just set it to null no? I think that building everything by default is not a good idea.

[Mic92]

You should be able to just set it to null no? I think that building everything by default is not a good idea.

I think this was just for testing not intended as the new default.

[Mic92]

Should we mention here that this in addition to the buildbot github topic?

[zowoq]

You should be able to just set it to null no? I think that building everything by default is not a good idea.

I think this was just for testing not intended as the new default.

Was kind of thinking of a new default. Could have an assert requiring that one or more of topic, userAllowlist, repoAllowlist is set? But maybe not be worth the disruption for other users.