Supply more structured info in sync errors

Instead of using a map, which forces us to give a glommed-together
string as the key (so that it can be JSONed), use a slice of structs
with the unglommed data.

daemon/loop.go

@@ -193,15 +193,18 @@ func (d *Daemon) doSync(logger log.Logger) (retErr error) {
 		return errors.Wrap(err, "loading resources from repo")
 	}
 
-	var syncErrors map[string]string
+	var syncErrors []event.ResourceError
 	// TODO supply deletes argument from somewhere (command-line?)
 	if err := fluxsync.Sync(d.Manifests, allResources, d.Cluster, false, logger); err != nil {
 		logger.Log("err", err)
 		switch syncerr := err.(type) {
 		case cluster.SyncError:
-			syncErrors = map[string]string{}
 			for _, e := range syncerr {
-				syncErrors[fmt.Sprintf("%s (%s)", e.ResourceID(), e.Source())] = e.Error.Error()
+				syncErrors = append(syncErrors, event.ResourceError{
+					ID:    e.ResourceID().String(),
+					Path:  e.Source(),
+					Error: e.Error.Error(),
+				})
 			}
 		default:
 			return err

event/event.go

@@ -195,6 +195,12 @@ type Commit struct {
 	Message  string `json:"message"`
 }
 
+type ResourceError struct {
+	ID    string
+	Path  string
+	Error string
+}
+
 // SyncEventMetadata is the metadata for when new a commit is synced to the cluster
 type SyncEventMetadata struct {
 	// for parsing old events; Commits is now used in preference
@@ -205,7 +211,7 @@ type SyncEventMetadata struct {
 	// ourselves)
 	Includes map[string]bool `json:"includes,omitempty"`
 	// Per-resource errors
-	Errors map[string]string `json:"errors,omitempty"`
+	Errors []ResourceError `json:"errors,omitempty"`
 	// `true` if we have no record of having synced before
 	InitialSync bool `json:"initialSync,omitempty"`
 }