Queueing, prepping to fetch

A lot more to go, but this is the core.

Need to think about how to test the queue handlers.

internal/types/constants.go

@@ -0,0 +1,9 @@
+package types
+
+type UpdateFrequency string
+
+const (
+	UPDATE_DAILY   UpdateFrequency = "DAILY"
+	UPDATE_WEEKLY  UpdateFrequency = "WEEKLY"
+	UPDATE_MONTHLY UpdateFrequency = "MONTHLY"
+)