Added a "Published in the last X days" filter, applied by the backend

GET /api/opportunities takes released_from, an RFC 3339 time, and lists
only the opportunities whose latest release is at or after it. It works
with paging and with changed_after, which keeps the same batch either
way; an invalid value is 400.

The frontend's filter defaults to 7 days, from midnight UK time, and
sends it with every load and catch-up, so a year of opportunities isn't
downloaded to show a week's. Changing the days loads the list again;
Clear filters goes back to 7.

internal/api/opportunities.go

@@ -7,6 +7,7 @@ import (
 	"reflect"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/go-chi/chi/v5"
 
@@ -71,7 +72,8 @@ func (h *opportunityRoutes) Routes(router chi.Router) {
 // list serves GET /opportunities: a page of opportunities, newest release
 // first, with their classifications and marks but not their releases. The
 // page is set by the offset and limit (default 50, at most 100) query
-// parameters. With changed_after, it serves the opportunities changed since
+// parameters, and released_from leaves out opportunities whose latest release
+// is before it. With changed_after, it serves the opportunities changed since
 // that batch instead (see listChanged).
 //
 //	@Summary		List opportunities
@@ -85,27 +87,38 @@ func (h *opportunityRoutes) Routes(router chi.Router) {
 //	@Description	releases or with changed marks), and batch is the newest
 //	@Description	batch they include. offset and limit can't be given with
 //	@Description	changed_after. An unknown batch is 410 Gone: reload the
-//	@Description	whole list.
+//	@Description	whole list. released_from (RFC 3339, inclusive) leaves out
+//	@Description	opportunities whose latest release is before it, in a page
+//	@Description	or with changed_after.
 //	@Tags			opportunities
 //	@Produce		json
 //	@Param			offset			query		int		false	"Opportunities to skip"	minimum(0)	default(0)
 //	@Param			limit			query		int		false	"Page size"				minimum(1)	maximum(100)	default(50)
 //	@Param			changed_after	query		string	false	"List the opportunities changed after this batch instead"
+//	@Param			released_from	query		string	false	"Only opportunities whose latest release is at or after this time"	format(date-time)
 //	@Success		200				{object}	OpportunityPage
-//	@Failure		400				{object}	httpx.Problem	"Invalid offset or limit, or either with changed_after"
+//	@Failure		400				{object}	httpx.Problem	"Invalid offset, limit or released_from, or offset or limit with changed_after"
 //	@Failure		410				{object}	httpx.Problem	"Unknown batch"
 //	@Failure		500				{object}	httpx.Problem
 //	@Router			/opportunities [get]
 func (h *opportunityRoutes) list(w http.ResponseWriter, r *http.Request) {
 	query := r.URL.Query()
+	releasedFrom, err := timeParam(
+		"released_from", query.Get("released_from"),
+	)
+	if err != nil {
+		httpx.WriteProblem(w, r, http.StatusBadRequest, err.Error())
+		return
+	}
+
 	if query.Has("changed_after") {
-		h.listChanged(w, r)
+		h.listChanged(w, r, releasedFrom)
 		return
 	}
 
 	offset, offsetErr := intParam(query.Get("offset"), 0, 0, 1<<30)
 	limit, limitErr := intParam(query.Get("limit"), 50, 1, 100)
-	err := errors.Join(offsetErr, limitErr)
+	err = errors.Join(offsetErr, limitErr)
 	if err != nil {
 		httpx.WriteProblem(w, r, http.StatusBadRequest, err.Error())
 		return
@@ -123,8 +136,9 @@ func (h *opportunityRoutes) list(w http.ResponseWriter, r *http.Request) {
 	opportunities, err := h.store.ListOpportunities(
 		r.Context(),
 		store.OpportunityFilter{
-			Limit:  limit + 1,
-			Offset: offset,
+			Limit:        limit + 1,
+			Offset:       offset,
+			ReleasedFrom: releasedFrom,
 		},
 	)
 	if err != nil {
@@ -148,10 +162,11 @@ func (h *opportunityRoutes) list(w http.ResponseWriter, r *http.Request) {
 
 // listChanged serves GET /opportunities?changed_after=batch: every
 // opportunity changed after the change batch, as one page, with the newest
-// batch it includes. An unknown batch, such as one from another database, is
-// 410 Gone, as the client can't catch up from it.
+// batch it includes, leaving out those whose latest release is before
+// releasedFrom unless it is zero. An unknown batch, such as one from another
+// database, is 410 Gone, as the client can't catch up from it.
 func (h *opportunityRoutes) listChanged(
-	w http.ResponseWriter, r *http.Request,
+	w http.ResponseWriter, r *http.Request, releasedFrom time.Time,
 ) {
 	query := r.URL.Query()
 	if query.Has("offset") || query.Has("limit") {
@@ -165,7 +180,7 @@ func (h *opportunityRoutes) listChanged(
 	}
 
 	opportunities, batch, err := h.store.ListChangedOpportunities(
-		r.Context(), query.Get("changed_after"),
+		r.Context(), query.Get("changed_after"), releasedFrom,
 	)
 	if errors.Is(err, store.ErrUnknownBatch) {
 		httpx.WriteProblem(