Added api/classifications endpoint, requiring a new query

internal/api/classifications.go

@@ -0,0 +1,54 @@
+package api
+
+import (
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+
+	"git.avsdev.uk/Go/job-search/internal/httpx"
+	"git.avsdev.uk/Go/job-search/internal/store"
+)
+
+// classificationRoutes wires HTTP handlers to the classification codes in
+// the opportunity store. They're read-only.
+type classificationRoutes struct {
+	store *store.Store
+}
+
+// newClassificationRoutes returns the classification handlers for
+// opportunityStore.
+func newClassificationRoutes(
+	opportunityStore *store.Store,
+) *classificationRoutes {
+	return &classificationRoutes{
+		store: opportunityStore,
+	}
+}
+
+// Routes registers the classification routes on router (mounted under
+// /api).
+func (h *classificationRoutes) Routes(router chi.Router) {
+	router.Get("/classifications", h.list)
+}
+
+// list serves GET /classifications: every classification code that at least
+// one opportunity has, ordered by code.
+//
+//	@Summary		List classifications
+//	@Description	Every classification code (CPV and others) that at least one
+//	@Description	stored opportunity has, once each, ordered by code: the
+//	@Description	codes worth filtering opportunities by.
+//	@Tags			classifications
+//	@Produce		json
+//	@Success		200	{array}		types.ClassificationCode
+//	@Failure		500	{object}	httpx.Problem
+//	@Router			/classifications [get]
+func (h *classificationRoutes) list(w http.ResponseWriter, r *http.Request) {
+	classifications, err := h.store.ListClassifications(r.Context())
+	if err != nil {
+		httpx.WriteProblem(w, r, http.StatusInternalServerError, "")
+		return
+	}
+
+	httpx.WriteJSON(w, http.StatusOK, classifications)
+}