gnu: Add elixir-tz.

* gnu/packages/elixir-web.scm (elixir-tz): New variable.

Change-Id: I81781fd33c7274174f69a4c2543b809892d2a609
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/packages/elixir-web.scm

@@ -215,6 +215,25 @@ show some high-level examples and introduce the Plug's main building blocks.")
     (home-page "https://hexdocs.pm/plug/")
     (license license:asl2.0)))
 
+;; This package lives here to avoid module level circular dependencies as it
+;; depends on elixir-mint.
+(define-public elixir-tz
+  (package
+    (name "elixir-tz")
+    (version "0.28.1")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (hexpm-uri "tz" version))
+       (sha256
+        (base32 "12lchkhdxbv8ai09i2lsy394yx1xrfq1yz5p8dn3qr0236ma3p5z"))))
+    (build-system mix-build-system)
+    (propagated-inputs (list elixir-castore elixir-mint))
+    (synopsis "Time zone support for Elixir")
+    (description "Time zone support for Elixir.")
+    (home-page "https://hexdocs.pm/tz/")
+    (license license:asl2.0)))
+
 (define-public elixir-websock
   (package
     (name "elixir-websock")