An optional dependency is optional at activation, not at compile time: importing the package that declares a looked-up type keeps the other plugin in go.mod; only party.Plugin.Requires leaves it out.
- 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