Flakeify home config

Use nix flakes instead of niv for pinning dependency channels.

First step towards merging my "nixos-system" and "nixos-home"
configs into a single trivially reproducible flake setup.

Apply home config via:

> nix build .#homeManagerConfigurations.common.activationPackage --impure
> ./result/activate

1 files changed, 6 insertions, 4 deletions

diff --git a/gui/email.nix b/gui/email.nix
index b1f3f0d..46d1731 100644
--- a/gui/email.nix
+++ b/gui/email.nix
@@ -1,15 +1,17 @@
 { pkgs, ... }:
 
 {
-  programs.mbsync.enable = true;
-  programs.msmtp.enable = true;
+  programs = {
+    mbsync.enable = true;
+    msmtp.enable = true;
+  };
 
   accounts.email = {
     maildirBasePath = "mail";
-    
+
     accounts.automatix = {
       primary = true;
-      
+
       realName = "Adrian Kummerländer";
       address  = "adrian@kummerlaender.eu";