v2: Module documentation; refactor LoadModule(); new caddy struct tags (#2924)

This commit goes a long way toward making automated documentation of
Caddy config and Caddy modules possible. It's a broad, sweeping change,
but mostly internal. It allows us to automatically generate docs for all
Caddy modules (including future third-party ones) and make them viewable
on a web page; it also doubles as godoc comments.

As such, this commit makes significant progress in migrating the docs
from our temporary wiki page toward our new website which is still under
construction.

With this change, all host modules will use ctx.LoadModule() and pass in
both the struct pointer and the field name as a string. This allows the
reflect package to read the struct tag from that field so that it can
get the necessary information like the module namespace and the inline
key.

This has the nice side-effect of unifying the code and documentation. It
also simplifies module loading, and handles several variations on field
types for raw module fields (i.e. variations on json.RawMessage, such as
arrays and maps).

I also renamed ModuleInfo.Name -> ModuleInfo.ID, to make it clear that
the ID is the "full name" which includes both the module namespace and
the name. This clarity is helpful when describing module hierarchy.

As of this change, Caddy modules are no longer an experimental design.
I think the architecture is good enough to go forward.

1 files changed, 11 insertions, 6 deletions

diff --git a/modules/caddytls/distributedstek/distributedstek.go b/modules/caddytls/distributedstek/distributedstek.go
index a0c4cd2..cef3733 100644
--- a/modules/caddytls/distributedstek/distributedstek.go
+++ b/modules/caddytls/distributedstek/distributedstek.go
@@ -39,9 +39,15 @@ func init() {
 	caddy.RegisterModule(Provider{})
 }
 
-// Provider implements a distributed STEK provider.
+// Provider implements a distributed STEK provider. This
+// module will obtain STEKs from a storage module instead
+// of generating STEKs internally. This allows STEKs to be
+// coordinated, improving TLS session resumption in a cluster.
 type Provider struct {
-	Storage json.RawMessage `json:"storage,omitempty"`
+	// The storage module wherein to store and obtain session
+	// ticket keys. If unset, Caddy's default/global-configured
+	// storage module will be used.
+	Storage json.RawMessage `json:"storage,omitempty" caddy:"namespace=caddy.storage inline_key=module"`
 
 	storage    certmagic.Storage
 	stekConfig *caddytls.SessionTicketService
@@ -51,8 +57,8 @@ type Provider struct {
 // CaddyModule returns the Caddy module information.
 func (Provider) CaddyModule() caddy.ModuleInfo {
 	return caddy.ModuleInfo{
-		Name: "tls.stek.distributed",
-		New:  func() caddy.Module { return new(Provider) },
+		ID:  "tls.stek.distributed",
+		New: func() caddy.Module { return new(Provider) },
 	}
 }
 
@@ -60,7 +66,7 @@ func (Provider) CaddyModule() caddy.ModuleInfo {
 func (s *Provider) Provision(ctx caddy.Context) error {
 	// unpack the storage module to use, if different from the default
 	if s.Storage != nil {
-		val, err := ctx.LoadModuleInline("module", "caddy.storage", s.Storage)
+		val, err := ctx.LoadModule(s, "Storage")
 		if err != nil {
 			return fmt.Errorf("loading TLS storage module: %s", err)
 		}
@@ -69,7 +75,6 @@ func (s *Provider) Provision(ctx caddy.Context) error {
 			return fmt.Errorf("creating TLS storage configuration: %v", err)
 		}
 		s.storage = cmStorage
-		s.Storage = nil // allow GC to deallocate
 	}
 
 	// otherwise, use default storage