Added api/classifications endpoint, requiring a new query

internal/api/api.go

@@ -20,7 +20,8 @@ type API struct {
 type Option func(*API)
 
 // WithStore makes the API serve the opportunities in opportunityStore under
-// /opportunities. Without it there are no opportunity routes.
+// /opportunities, and their classifications under /classifications. Without
+// it there are neither.
 func WithStore(opportunityStore *store.Store) Option {
 	return func(a *API) {
 		a.store = opportunityStore
@@ -46,10 +47,12 @@ func New(opts ...Option) *API {
 }
 
 // Routes registers the API's routes on router (mounted under /api): its
-// description (see openapi.go), and the opportunities if it has a store.
+// description (see openapi.go), and the opportunities and classifications if
+// it has a store.
 func (a *API) Routes(router chi.Router) {
 	docsRoutes(router)
 	if a.store != nil {
 		newOpportunityRoutes(a.store, a.events).Routes(router)
+		newClassificationRoutes(a.store).Routes(router)
 	}
 }