MRSK hooks

Adds hooks to MRSK. Currently just two hooks, pre-build and post-push.

We could break the build and push into two separate commands if we
found the need for post-build and/or pre-push hooks.

Hooks are stored in `.mrsk/hooks`. Running `mrsk init` will now create
that folder and add sample hook scripts.

Hooks returning non-zero exit codes will abort the current command.

Further potential work here:
- We could replace the audit broadcast command with a
post-deploy/post-rollback hook or similar
- Maybe provide pre-command/post-command hooks that run after every
mrsk invocation
- Also look for hooks in `~/.mrsk/hooks`

test/integration/integration_test.rb

@@ -3,6 +3,7 @@ require "test_helper"
 
 class IntegrationTest < ActiveSupport::TestCase
   setup do
+    ENV["TEST_ID"] = SecureRandom.hex
     docker_compose "up --build -d"
     wait_for_healthy
     setup_deployer
@@ -14,7 +15,7 @@ class IntegrationTest < ActiveSupport::TestCase
 
   private
     def docker_compose(*commands, capture: false, raise_on_error: true)
-      command = "docker compose #{commands.join(" ")}"
+      command = "TEST_ID=#{ENV["TEST_ID"]} docker compose #{commands.join(" ")}"
       succeeded = false
       if capture
         result = stdouted { succeeded = system("cd test/integration && #{command}") }
@@ -82,6 +83,13 @@ class IntegrationTest < ActiveSupport::TestCase
       assert_equal version, response.body.strip
     end
 
+    def assert_hooks_ran
+      [ "pre-build", "post-push" ].each do |hook|
+        file = "/tmp/#{ENV["TEST_ID"]}/#{hook}"
+        assert_match /File: #{file}/, deployer_exec("stat #{file}", capture: true)
+      end
+    end
+
     def wait_for_healthy(timeout: 20)
       timeout_at = Time.now + timeout
       while docker_compose("ps -a | tail -n +2 | grep -v '(healthy)' | wc -l", capture: true) != "0"