Configuration tweaks (#2567)

This makes the following changes:

* The various `Defaults` functions are now responsible for setting sane defaults if `generate` is specified, rather than hiding them in `generate-config`
* Some configuration options have been marked as `omitempty` so that they don't appear in generated configs unnecessarily (monolith-specific vs. polylith-specific options)
* A new option `-polylith` has been added to `generate-config` to create a config that makes sense for polylith deployments (i.e. including the internal/external API listeners and per-component database sections)
* A new option `-normalise` has been added to `generate-config` to take an existing file and add any missing options and/or defaults

setup/config/config.go

@@ -211,7 +211,10 @@ func loadConfig(
 	monolithic bool,
 ) (*Dendrite, error) {
 	var c Dendrite
-	c.Defaults(false)
+	c.Defaults(DefaultOpts{
+		Generate:   false,
+		Monolithic: monolithic,
+	})
 	c.IsMonolith = monolithic
 
 	var err error
@@ -295,21 +298,25 @@ func (config *Dendrite) Derive() error {
 	return nil
 }
 
+type DefaultOpts struct {
+	Generate   bool
+	Monolithic bool
+}
+
 // SetDefaults sets default config values if they are not explicitly set.
-func (c *Dendrite) Defaults(generate bool) {
+func (c *Dendrite) Defaults(opts DefaultOpts) {
 	c.Version = Version
 
-	c.Global.Defaults(generate)
-	c.ClientAPI.Defaults(generate)
-	c.FederationAPI.Defaults(generate)
-	c.KeyServer.Defaults(generate)
-	c.MediaAPI.Defaults(generate)
-	c.RoomServer.Defaults(generate)
-	c.SyncAPI.Defaults(generate)
-	c.UserAPI.Defaults(generate)
-	c.AppServiceAPI.Defaults(generate)
-	c.MSCs.Defaults(generate)
-
+	c.Global.Defaults(opts)
+	c.ClientAPI.Defaults(opts)
+	c.FederationAPI.Defaults(opts)
+	c.KeyServer.Defaults(opts)
+	c.MediaAPI.Defaults(opts)
+	c.RoomServer.Defaults(opts)
+	c.SyncAPI.Defaults(opts)
+	c.UserAPI.Defaults(opts)
+	c.AppServiceAPI.Defaults(opts)
+	c.MSCs.Defaults(opts)
 	c.Wiring()
 }