Add attribute flag building and parsing (#1562)

This adds a few command sketches but that's not the main point of the PR
and filling those out will come in a different PR. This adds a new flag
type that can combine inputs to a single target slice, retaining the
ability to distinguish where it came from but also keep ordering across
different flag names. It also implements a function that does the
heuristic parsing with fallback.

internal/host/plugin/repository_host_set.go

@@ -373,14 +373,14 @@ func (r *Repository) Endpoints(ctx context.Context, setIds []string) ([]*host.En
 
 	type setInfo struct {
 		preferredEndpoint endpoint.Option
-		plgSet *pb.HostSet
+		plgSet            *pb.HostSet
 	}
 
-	type catalogInfo struct{
-		publicId string
-		plg plgpb.HostPluginServiceServer
-		setInfos map[string]*setInfo
-		plgCat *hcpb.HostCatalog
+	type catalogInfo struct {
+		publicId  string
+		plg       plgpb.HostPluginServiceServer
+		setInfos  map[string]*setInfo
+		plgCat    *hcpb.HostCatalog
 		persisted *plgpb.HostCatalogPersisted
 	}
 
@@ -458,10 +458,10 @@ func (r *Repository) Endpoints(ctx context.Context, setIds []string) ([]*host.En
 			sets = append(sets, si.plgSet)
 		}
 
-		resp, err := ci.plg.ListHosts(ctx,  &plgpb.ListHostsRequest{
+		resp, err := ci.plg.ListHosts(ctx, &plgpb.ListHostsRequest{
 			Catalog: ci.plgCat,
 			Sets:    sets,
-			//Persisted: ci.persisted,
+			// Persisted: ci.persisted,
 		})
 		if err != nil {
 			return nil, errors.Wrap(ctx, err, op)

internal/host/plugin/repository_host_set_test.go

@@ -389,7 +389,7 @@ func TestRepository_Endpoints(t *testing.T) {
 				}
 				return &plgpb.ListHostsResponse{Hosts: []*plgpb.ListHostsResponseHost{
 					{
-						SetIds: setIds,
+						SetIds:      setIds,
 						ExternalId:  "test",
 						IpAddresses: []string{"10.0.0.5", "192.168.0.5"},
 						DnsNames:    nil,
@@ -407,7 +407,7 @@ func TestRepository_Endpoints(t *testing.T) {
 
 	tests := []struct {
 		name      string
-		setIds     []string
+		setIds    []string
 		want      []*host.Endpoint
 		wantIsErr errors.Code
 	}{
@@ -416,7 +416,7 @@ func TestRepository_Endpoints(t *testing.T) {
 			wantIsErr: errors.InvalidParameter,
 		},
 		{
-			name:  "with-set10",
+			name:   "with-set10",
 			setIds: []string{hostSet10.GetPublicId()},
 			want: []*host.Endpoint{
 				{
@@ -431,7 +431,7 @@ func TestRepository_Endpoints(t *testing.T) {
 			},
 		},
 		{
-			name:  "with-different-set",
+			name:   "with-different-set",
 			setIds: []string{hostSet192.GetPublicId()},
 			want: []*host.Endpoint{
 				{
@@ -446,14 +446,14 @@ func TestRepository_Endpoints(t *testing.T) {
 			},
 		},
 		{
-			name:  "with-all-addresses-filtered-set",
+			name:   "with-all-addresses-filtered-set",
 			setIds: []string{hostSet100.GetPublicId()},
-			want:  nil,
+			want:   nil,
 		},
 		{
-			name:  "with-no-hosts-from-plugin",
+			name:   "with-no-hosts-from-plugin",
 			setIds: []string{hostlessSet.GetPublicId()},
-			want:  nil,
+			want:   nil,
 		},
 	}