config: introduce the concept of DevConfig

In this commit, we introduce a DevConfig struct which is embedded in the
main lit Config struct. It is defined in two separate files that are
made mutually exclusive using the `dev` build tag. The idea of this
struct is that it allows us to expose additional config options to LiT
if we build in a development environment such as our itests. In other
words, we will be able to start developing features and testing them
before making them available to users via the production build.

As of this commit, both implementations of the struct are the same.

config_dev.go

@@ -0,0 +1,38 @@
+//go:build dev
+
+package terminal
+
+import (
+	"path/filepath"
+
+	"github.com/lightninglabs/lightning-terminal/accounts"
+	"github.com/lightningnetwork/lnd/clock"
+)
+
+// DevConfig is a struct that holds the configuration options for a development
+// environment. The purpose of this struct is to hold config options for
+// features not yet available in production. Since our itests are built with
+// the dev tag, we can test these features in our itests.
+//
+// nolint:lll
+type DevConfig struct {
+}
+
+// Validate checks that all the values set in our DevConfig are valid and uses
+// the passed parameters to override any defaults if necessary.
+func (c *DevConfig) Validate(dbDir, network string) error {
+	return nil
+}
+
+// defaultDevConfig returns a new DevConfig with default values set.
+func defaultDevConfig() *DevConfig {
+	return &DevConfig{}
+}
+
+// NewAccountStore creates a new account store based on the chosen database
+// backend.
+func NewAccountStore(cfg *Config, clock clock.Clock) (accounts.Store, error) {
+	return accounts.NewBoltStore(
+		filepath.Dir(cfg.MacaroonPath), accounts.DBFilename, clock,
+	)
+}