feat(11.1-03): add the Architecture and Plugins docs sections

- architecture: introduction, Go modules and workspaces, application
  lifecycle, request lifecycle
- plugins: registration, scheduling, extending, testing
- verified Examples for backpack services, towel request context,
  pact schedules and festival events
- TestDocsRequiredPages lists the eight new pages

modules/pact/example_test.go

@@ -0,0 +1,37 @@
+package pact_test
+
+import (
+	"fmt"
+	"time"
+
+	"git.golem15.com/golem15/summercms/modules/pact"
+)
+
+// BlogPlugin is the acme.blog plugin; only its schedule is shown here.
+type BlogPlugin struct{}
+
+var _ pact.HasSchedule = (*BlogPlugin)(nil)
+
+// Schedule runs three of the plugin's registered console commands.
+func (p *BlogPlugin) Schedule() []pact.ScheduledCommand {
+	return []pact.ScheduledCommand{
+		{Command: "blog:prune-drafts", Cadence: pact.Daily()},
+		{Command: "blog:send-digest", Cadence: pact.DailyAt(7, 30)},
+		{Command: "blog:sync-feed", Args: []string{"--quiet"}, Cadence: pact.Every(15 * time.Minute)},
+	}
+}
+
+func ExampleHasSchedule() {
+	var plugin pact.HasSchedule = &BlogPlugin{}
+	for _, entry := range plugin.Schedule() {
+		if hour, minute, daily := entry.Cadence.At(); daily {
+			fmt.Printf("%s %v: daily at %02d:%02d\n", entry.Command, entry.Args, hour, minute)
+			continue
+		}
+		fmt.Printf("%s %v: every %s\n", entry.Command, entry.Args, entry.Cadence.Interval())
+	}
+	// Output:
+	// blog:prune-drafts []: daily at 00:00
+	// blog:send-digest []: daily at 07:30
+	// blog:sync-feed [--quiet]: every 15m0s
+}