Internal state persistence (#27)

Allow us to generate year over year reports without having to rerun everything from the beginning.

Co-authored-by: Natercio Moniz <[email protected]>

internal/ephemeral_store.go

@@ -0,0 +1,14 @@
+package internal
+
+import "context"
+
+// EphemeralStore loads an empty state and discards everything on save.
+type EphemeralStore struct{}
+
+func (EphemeralStore) Load(context.Context) (map[string]*FillerQueue, error) {
+	return make(map[string]*FillerQueue), nil
+}
+
+func (EphemeralStore) Save(context.Context, map[string]*FillerQueue) error {
+	return nil
+}