Copy Puma systemd unit template from capistrano3-puma

This commit copies the default puma.service.erb template from the
capistrano3-puma gem into lib/capistrano/templates. This allows us to
customize the generated systemd unit file during deploy.

Note that we are also removing the `:puma_conf` variable from `config/deploy.rb`,
as the new ExecStart line in the systemd template (based on capistrano3-puma 6.0.0)
does not rely on a separate Puma config file. The command now directly invokes:

  ExecStart=<%= expanded_bundle_command %> exec puma -e <%= fetch(:puma_env) %>

This replaces the older format used in 5.2.0:

  ExecStart=<%= expanded_bundle_command %> exec --keep-file-descriptors puma -C <%= fetch(:puma_conf) %>

which required explicitly setting the Puma config path.

.erb_lint.yml

@@ -2,6 +2,7 @@
 EnableDefaultLinters: false
 exclude:
   - '**/vendor/**/*'
+  - 'lib/capistrano/templates/*'
 linters:
   AllowedScriptType:
     enabled: true

config/deploy.rb

@@ -49,7 +49,6 @@ set :fnm_setup_command, -> do
 set :fnm_install_node_command, -> { "#{fetch(:fnm_setup_command)} && fnm use --install-if-missing" }
 set :fnm_map_bins, %w[node npm rake yarn]
 
-set :puma_conf, "#{release_path}/config/puma/#{fetch(:rails_env)}.rb"
 set :puma_systemctl_user, :user
 set :puma_enable_socket_service, true
 set :puma_service_unit_env_vars, ["EXECJS_RUNTIME=Disabled"]

lib/capistrano/templates/puma.service.erb

@@ -0,0 +1,40 @@
+# This file tells systemd how to run Puma as a 24/7 long-running daemon.
+#
+# Customize this file based on your bundler location, app directory, etc.
+# Customize and copy this into /usr/lib/systemd/system (CentOS) or /lib/systemd/system (Ubuntu).
+# Then run:
+#   - systemctl enable <%= fetch(:puma_service_unit_name) %>
+#   - systemctl {start,stop,restart} <%= fetch(:puma_service_unit_name) %>
+#
+#
+# Use `journalctl -u <%= fetch(:puma_service_unit_name) %> -rn 100` to view the last 100 lines of log output.
+#
+[Unit]
+Description=Puma HTTP Server for <%= "#{fetch(:application)} (#{fetch(:stage)})" %>
+<%= "Requires=#{fetch(:puma_service_unit_name)}.socket" if fetch(:puma_enable_socket_service) %>
+After=syslog.target network.target
+
+[Service]
+Type=<%= service_unit_type %>
+WatchdogSec=10
+<%="User=#{puma_user(@role)}" if fetch(:puma_systemctl_user) == :system %>
+WorkingDirectory=<%= current_path %>
+ExecStart=<%= expanded_bundle_command %> exec puma -e <%= fetch(:puma_env) %>
+ExecReload=/bin/kill -USR1 $MAINPID
+<%- Array(fetch(:puma_service_unit_env_files)).each do |file| %>
+<%="EnvironmentFile=#{file}" -%>
+<% end -%>
+<% Array(fetch(:puma_service_unit_env_vars)).each do |environment_variable| %>
+<%="Environment=\"#{environment_variable}\"" -%>
+<% end -%>
+
+# if we crash, restart
+RestartSec=1
+Restart=on-failure
+
+<%="StandardOutput=append:#{fetch(:puma_access_log)}" if fetch(:puma_access_log) %>
+<%="StandardError=append:#{fetch(:puma_error_log)}" if fetch(:puma_error_log) %>
+
+SyslogIdentifier=<%= fetch(:puma_service_unit_name) %>
+[Install]
+WantedBy=<%=(fetch(:puma_systemctl_user) == :system) ? "multi-user.target" : "default.target"%>