refactor: Decouple router and handlers (#31)

* refactor: decouple router to allow adding custom log and input data handlers

* feat: refactor handlers

* devops: update service build args

* chore: cleanup unecessary files/code

internal/handler/handler.go

@@ -0,0 +1,13 @@
+package handler
+
+import "github.com/grassrootseconomics/celo-tracker/internal/cache"
+
+type HandlerContainer struct {
+	cache cache.Cache
+}
+
+func New(cacheProvider cache.Cache) *HandlerContainer {
+	return &HandlerContainer{
+		cache: cacheProvider,
+	}
+}