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, 17 insertions, 7 deletions

diff --git a/modules/caddytls/sessiontickets.go b/modules/caddytls/sessiontickets.go
index 6ca921d..258c135 100644
--- a/modules/caddytls/sessiontickets.go
+++ b/modules/caddytls/sessiontickets.go
@@ -28,11 +28,22 @@ import (
 
 // SessionTicketService configures and manages TLS session tickets.
 type SessionTicketService struct {
-	KeySource        json.RawMessage `json:"key_source,omitempty"`
-	RotationInterval caddy.Duration  `json:"rotation_interval,omitempty"`
-	MaxKeys          int             `json:"max_keys,omitempty"`
-	DisableRotation  bool            `json:"disable_rotation,omitempty"`
-	Disabled         bool            `json:"disabled,omitempty"`
+	// KeySource is the method by which Caddy produces or obtains
+	// TLS session ticket keys (STEKs). By default, Caddy generates
+	// them internally using a secure pseudorandom source.
+	KeySource json.RawMessage `json:"key_source,omitempty" caddy:"namespace=tls.stek inline_key=provider"`
+
+	// How often Caddy rotates STEKs. Default: 12h.
+	RotationInterval caddy.Duration `json:"rotation_interval,omitempty"`
+
+	// The maximum number of keys to keep in rotation. Default: 4.
+	MaxKeys int `json:"max_keys,omitempty"`
+
+	// Disables STEK rotation.
+	DisableRotation bool `json:"disable_rotation,omitempty"`
+
+	// Disables TLS session resumption by tickets.
+	Disabled bool `json:"disabled,omitempty"`
 
 	keySource   STEKProvider
 	configs     map[*tls.Config]struct{}
@@ -57,12 +68,11 @@ func (s *SessionTicketService) provision(ctx caddy.Context) error {
 	}
 
 	// load the STEK module, which will provide keys
-	val, err := ctx.LoadModuleInline("provider", "tls.stek", s.KeySource)
+	val, err := ctx.LoadModule(s, "KeySource")
 	if err != nil {
 		return fmt.Errorf("loading TLS session ticket ephemeral keys provider module: %s", err)
 	}
 	s.keySource = val.(STEKProvider)
-	s.KeySource = nil // allow GC to deallocate
 
 	// if session tickets or just rotation are
 	// disabled, no need to start service