discourse: Add a proper plugin builder + a few initial packages

Some discourse plugins have Ruby dependencies and require a
specialized builder. This introduces a generic builder that can be
used whether the plugin has Ruby dependencies or not. It also adds a
set of pre-packaged plugins available through `discourse.plugins` and
provides an easy way to add more.

(cherry picked from commit 7671b90919af8271bdf7e07bb86d63216a2145d6)

pkgs/servers/web-apps/discourse/plugins/discourse-github/Gemfile

@@ -0,0 +1,3 @@
+source 'https://rubygems.org'
+gem 'sawyer', '0.8.2'
+gem 'octokit', '4.21.0'

pkgs/servers/web-apps/discourse/plugins/discourse-github/Gemfile.lock

@@ -0,0 +1,37 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    addressable (2.7.0)
+      public_suffix (>= 2.0.2, < 5.0)
+    faraday (1.4.2)
+      faraday-em_http (~> 1.0)
+      faraday-em_synchrony (~> 1.0)
+      faraday-excon (~> 1.1)
+      faraday-net_http (~> 1.0)
+      faraday-net_http_persistent (~> 1.1)
+      multipart-post (>= 1.2, < 3)
+      ruby2_keywords (>= 0.0.4)
+    faraday-em_http (1.0.0)
+    faraday-em_synchrony (1.0.0)
+    faraday-excon (1.1.0)
+    faraday-net_http (1.0.1)
+    faraday-net_http_persistent (1.1.0)
+    multipart-post (2.1.1)
+    octokit (4.21.0)
+      faraday (>= 0.9)
+      sawyer (~> 0.8.0, >= 0.5.3)
+    public_suffix (4.0.6)
+    ruby2_keywords (0.0.4)
+    sawyer (0.8.2)
+      addressable (>= 2.3.5)
+      faraday (> 0.8, < 2.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  octokit (= 4.21.0)
+  sawyer (= 0.8.2)
+
+BUNDLED WITH
+   2.1.4

pkgs/servers/web-apps/discourse/plugins/discourse-github/default.nix

@@ -0,0 +1,12 @@
+{ mkDiscoursePlugin, fetchFromGitHub }:
+
+mkDiscoursePlugin {
+  name = "discourse-github";
+  bundlerEnvArgs.gemdir = ./.;
+  src = fetchFromGitHub {
+    owner = "discourse";
+    repo = "discourse-github";
+    rev = "151e353a5a1971157c70c2e2b0f56387f212a81f";
+    sha256 = "00kra6zd2k1f2vwcdvxnxnammzh72f5qxcqbb94m0z6maj598wdy";
+  };
+}

pkgs/servers/web-apps/discourse/plugins/discourse-github/gemset.nix

@@ -0,0 +1,126 @@
+{
+  addressable = {
+    dependencies = ["public_suffix"];
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "1fvchp2rhp2rmigx7qglf69xvjqvzq7x0g49naliw29r2bz656sy";
+      type = "gem";
+    };
+    version = "2.7.0";
+  };
+  faraday = {
+    dependencies = ["faraday-em_http" "faraday-em_synchrony" "faraday-excon" "faraday-net_http" "faraday-net_http_persistent" "multipart-post" "ruby2_keywords"];
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "07mhk70gv453pg38md346470hknyhipdqppnplq706ll3k3lzb7v";
+      type = "gem";
+    };
+    version = "1.4.2";
+  };
+  faraday-em_http = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "12cnqpbak4vhikrh2cdn94assh3yxza8rq2p9w2j34bqg5q4qgbs";
+      type = "gem";
+    };
+    version = "1.0.0";
+  };
+  faraday-em_synchrony = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "1vgrbhkp83sngv6k4mii9f2s9v5lmp693hylfxp2ssfc60fas3a6";
+      type = "gem";
+    };
+    version = "1.0.0";
+  };
+  faraday-excon = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "0h09wkb0k0bhm6dqsd47ac601qiaah8qdzjh8gvxfd376x1chmdh";
+      type = "gem";
+    };
+    version = "1.1.0";
+  };
+  faraday-net_http = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "1fi8sda5hc54v1w3mqfl5yz09nhx35kglyx72w7b8xxvdr0cwi9j";
+      type = "gem";
+    };
+    version = "1.0.1";
+  };
+  faraday-net_http_persistent = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "0l2c835wl7gv34xp49fhd1bl4czkpw2g3ahqsak2251iqv5589ka";
+      type = "gem";
+    };
+    version = "1.1.0";
+  };
+  multipart-post = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "1zgw9zlwh2a6i1yvhhc4a84ry1hv824d6g2iw2chs3k5aylpmpfj";
+      type = "gem";
+    };
+    version = "2.1.1";
+  };
+  octokit = {
+    dependencies = ["faraday" "sawyer"];
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "0ak64rb48d8z98nw6q70r6i0i3ivv61iqla40ss5l79491qfnn27";
+      type = "gem";
+    };
+    version = "4.21.0";
+  };
+  public_suffix = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "1xqcgkl7bwws1qrlnmxgh8g4g9m10vg60bhlw40fplninb3ng6d9";
+      type = "gem";
+    };
+    version = "4.0.6";
+  };
+  ruby2_keywords = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "15wfcqxyfgka05v2a7kpg64x57gl1y4xzvnc9lh60bqx5sf1iqrs";
+      type = "gem";
+    };
+    version = "0.0.4";
+  };
+  sawyer = {
+    dependencies = ["addressable" "faraday"];
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "0yrdchs3psh583rjapkv33mljdivggqn99wkydkjdckcjn43j3cz";
+      type = "gem";
+    };
+    version = "0.8.2";
+  };
+}