Add github auth

Author: ericmj

config/runtime.exs

@@ -15,6 +15,8 @@ if config_env() == :prod do
     session_signing_salt: System.fetch_env!("HEXDOCS_SESSION_SIGNING_SALT"),
     session_encryption_salt: System.fetch_env!("HEXDOCS_SESSION_ENCRYPTION_SALT"),
     queue_concurrency: String.to_integer(System.fetch_env!("HEXDOCS_QUEUE_CONCURRENCY")),
+    github_user: System.fetch_env!("HEXDOCS_GITHUB_USER"),
+    github_token: System.fetch_env!("HEXDOCS_GITHUB_TOKEN"),
     host: System.fetch_env!("HEXDOCS_HOST")
 
   config :hexdocs, :repo_bucket, name: System.fetch_env!("HEXDOCS_REPO_BUCKET")

lib/hexdocs/source_repo/github.ex

@@ -4,14 +4,17 @@ defmodule Hexdocs.SourceRepo.GitHub do
 
   @impl true
   def versions(repo) do
+    user = Application.get_env(:hexdocs, :github_user)
+    token = Application.get_env(:hexdocs, :github_token)
     url = @github_url <> "/repos/#{repo}/tags"
 
     headers = [
       accept: "application/json"
     ]
 
     options = [
-      :with_body
+      :with_body,
+      basic_auth: {user, token}
     ]
 
     Hexdocs.HTTP.retry("github", url, fn ->