Merge pull request #8259 from Roasbeef/fn-module

fn: create new sub-module

fn/go.mod

@@ -0,0 +1,3 @@
+module github.com/lightningnetwork/lnd/fn
+
+go 1.19

go.mod

@@ -38,6 +38,7 @@ require (
 	github.com/lightningnetwork/lightning-onion v1.2.1-0.20230823005744-06182b1d7d2f
 	github.com/lightningnetwork/lnd/cert v1.2.2
 	github.com/lightningnetwork/lnd/clock v1.1.1
+	github.com/lightningnetwork/lnd/fn v0.0.0-00010101000000-000000000000
 	github.com/lightningnetwork/lnd/healthcheck v1.2.3
 	github.com/lightningnetwork/lnd/kvdb v1.4.4
 	github.com/lightningnetwork/lnd/queue v1.1.1
@@ -208,6 +209,8 @@ replace github.com/gogo/protobuf => github.com/gogo/protobuf v1.3.2
 // allows us to specify that as an option.
 replace google.golang.org/protobuf => github.com/lightninglabs/protobuf-go-hex-display v1.30.0-hex-display
 
+replace github.com/lightningnetwork/lnd/fn => ./fn
+
 // If you change this please also update .github/pull_request_template.md and
 // docs/INSTALL.md.
 go 1.19