Add `invites` flag in NodeInfo

This indicates whether or not invites are enabled on this instance. It
requires an upgrade to writefreely/go-nodeinfo v1.2.0

go.mod

@@ -62,7 +62,7 @@ require (
 	github.com/writeas/saturday v1.7.1
 	github.com/writeas/slug v1.2.0
 	github.com/writeas/web-core v1.0.0
-	github.com/writefreely/go-nodeinfo v1.1.0
+	github.com/writefreely/go-nodeinfo v1.2.0
 	golang.org/x/crypto v0.0.0-20190208162236-193df9c0f06f // indirect
 	golang.org/x/lint v0.0.0-20181217174547-8f45f776aaf1 // indirect
 	golang.org/x/net v0.0.0-20190206173232-65e2d4e15006 // indirect

go.sum

@@ -164,6 +164,8 @@ github.com/writeas/web-core v1.0.0 h1:5VKkCakQgdKZcbfVKJXtRpc5VHrkflusCl/KRCPzpQ
 github.com/writeas/web-core v1.0.0/go.mod h1:Si3chV7VWgY8CsV+3gRolMXSO2Vx1ZFAQ/mkrpvmyEE=
 github.com/writefreely/go-nodeinfo v1.1.0 h1:dp/ieEu0/gTeNKFvJTYhzBBouyFn7aiWtWzkb8J1JLg=
 github.com/writefreely/go-nodeinfo v1.1.0/go.mod h1:UTvE78KpcjYOlRHupZIiSEFcXHioTXuacCbHU+CAcPg=
+github.com/writefreely/go-nodeinfo v1.2.0 h1:La+YbTCvmpTwFhBSlebWDDL81N88Qf/SCAvRLR7F8ss=
+github.com/writefreely/go-nodeinfo v1.2.0/go.mod h1:UTvE78KpcjYOlRHupZIiSEFcXHioTXuacCbHU+CAcPg=
 golang.org/x/crypto v0.0.0-20180527072434-ab813273cd59 h1:hk3yo72LXLapY9EXVttc3Z1rLOxT9IuAPPX3GpY2+jo=
 golang.org/x/crypto v0.0.0-20180527072434-ab813273cd59/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190208162236-193df9c0f06f h1:ETU2VEl7TnT5bl7IvuKEzTDpplg5wzGYsOCAPhdoEIg=

nodeinfo.go

@@ -50,6 +50,7 @@ func nodeInfoConfig(db *datastore, cfg *config.Config) *nodeinfo.Config {
 			},
 			MaxBlogs:     cfg.App.MaxBlogs,
 			PublicReader: cfg.App.LocalTimeline,
+			Invites:      cfg.App.UserInvites != "",
 		},
 		Protocols: []nodeinfo.NodeProtocol{
 			nodeinfo.ProtocolActivityPub,