[feature] Cleanup unattached local media (#680)

* add localUnattached db function

* add parseOlderThan util function

* add pruneunusedlocalattachments to media manager

* add unusedlocal pruning to schedule + admin call

* set number of days to keep as a const

* fix test

internal/media/util.go

@@ -21,6 +21,7 @@ package media
 import (
 	"errors"
 	"fmt"
+	"time"
 
 	"github.com/h2non/filetype"
 	"github.com/sirupsen/logrus"
@@ -128,3 +129,19 @@ func (l *logrusWrapper) Info(msg string, keysAndValues ...interface{}) {
 func (l *logrusWrapper) Error(err error, msg string, keysAndValues ...interface{}) {
 	logrus.Error("media manager cron logger: ", err, msg, keysAndValues)
 }
+
+func parseOlderThan(olderThanDays int) (time.Time, error) {
+	// convert days into a duration string
+	olderThanHoursString := fmt.Sprintf("%dh", olderThanDays*24)
+
+	// parse the duration string into a duration
+	olderThanHours, err := time.ParseDuration(olderThanHoursString)
+	if err != nil {
+		return time.Time{}, err
+	}
+
+	// 'subtract' that from the time now to give our threshold
+	olderThan := time.Now().Add(-olderThanHours)
+
+	return olderThan, nil
+}