feat: use notifiers on schedule (#362)

* fix potential memory leak with time.After

* add new background service to manage scheduled notifications

* update docs

* remove old js reference

* closes #278

* tidy

backend/internal/core/services/service_background.go

@@ -0,0 +1,81 @@
+package services
+
+import (
+	"context"
+	"strings"
+	"time"
+
+	"github.com/containrrr/shoutrrr"
+	"github.com/hay-kot/homebox/backend/internal/data/repo"
+	"github.com/hay-kot/homebox/backend/internal/data/types"
+	"github.com/rs/zerolog/log"
+)
+
+type BackgroundService struct {
+	repos *repo.AllRepos
+}
+
+func (svc *BackgroundService) SendNotifiersToday(ctx context.Context) error {
+	// Get All Groups
+	groups, err := svc.repos.Groups.GetAllGroups(ctx)
+	if err != nil {
+		return err
+	}
+
+	today := types.DateFromTime(time.Now())
+
+	for i := range groups {
+		group := groups[i]
+
+		entries, err := svc.repos.MaintEntry.GetScheduled(ctx, group.ID, today)
+		if err != nil {
+			return err
+		}
+
+		if len(entries) == 0 {
+			log.Debug().
+				Str("group_name", group.Name).
+				Str("group_id", group.ID.String()).
+				Msg("No scheduled maintenance for today")
+			continue
+		}
+
+		notifiers, err := svc.repos.Notifiers.GetByGroup(ctx, group.ID)
+		if err != nil {
+			return err
+		}
+
+		urls := make([]string, len(notifiers))
+		for i := range notifiers {
+			urls[i] = notifiers[i].URL
+		}
+
+		bldr := strings.Builder{}
+
+		bldr.WriteString("Homebox Maintenance for (")
+		bldr.WriteString(today.String())
+		bldr.WriteString("):\n")
+
+		for i := range entries {
+			entry := entries[i]
+			bldr.WriteString(" - ")
+			bldr.WriteString(entry.Name)
+			bldr.WriteString("\n")
+		}
+
+		var sendErrs []error
+		for i := range urls {
+			err := shoutrrr.Send(urls[i], bldr.String())
+
+			if err != nil {
+				sendErrs = append(sendErrs, err)
+			}
+		}
+
+		if len(sendErrs) > 0 {
+			return sendErrs[0]
+		}
+	}
+
+	return nil
+}