fix(query): make WhereDelete compatible with ForceDelete

```go
db.NewDelete().Model((*Model)(nil)).Where("1 = 1").WhereDeleted().ForceDelete().Exec(ctx)
// Before this commit: DELETE FROM model WHERE 1 = 1
// After this commit:  DELETE FROM model WHERE 1 = 1 AND deleted_at IS NOT NULL
```

Additionally, the `Where("1 = 1")` trick is no longer required as `WhereDeleted()`
counts as a WHERE clause in mustAppendWhere.

```go
db.NewDelete().Model((*Model)(nil)).WhereDeleted().ForceDelete().Exec(ctx)
// Before this commit: Errors with "bun: Update and Delete queries require at least one Where"
// After this commit:  DELETE FROM model WHERE deleted_at IS NOT NULL
```

This gives us an easy and natural way to hard delete all soft deleted records.

Fixes issue uptrace#673.

internal/dbtest/soft_delete_test.go

@@ -111,15 +111,48 @@ func testSoftDeleteForce(t *testing.T, db *bun.DB) {
 	err := db.ResetModel(ctx, (*Video)(nil))
 	require.NoError(t, err)
 
-	video1 := &Video{
-		ID: 1,
+	videos := []Video{
+		{Name: "video1"},
+		{Name: "video2"},
+		{Name: "video3"},
 	}
-	_, err = db.NewInsert().Model(video1).Exec(ctx)
+
+	_, err = db.NewInsert().Model(&videos).Exec(ctx)
 	require.NoError(t, err)
 
-	_, err = db.NewDelete().Model(video1).WherePK().ForceDelete().Exec(ctx)
+	// Force delete video1.
+	_, err = db.NewDelete().Model((*Video)(nil)).Where("name = ?", "video1").ForceDelete().Exec(ctx)
+	require.NoError(t, err)
+
+	// Soft delete video2.
+	_, err = db.NewDelete().Model((*Video)(nil)).Where("name = ?", "video2").Exec(ctx)
+	require.NoError(t, err)
+
+	// Check one visible video.
+	var res []Video
+	err = db.NewSelect().Model((*Video)(nil)).Column("name").Scan(ctx, &res)
+	require.NoError(t, err)
+	require.Equal(t, []Video{{Name: "video3"}}, res)
+
+	// Check one soft deleted video.
+	err = db.NewSelect().Model((*Video)(nil)).Column("name").WhereDeleted().Scan(ctx, &res)
+	require.NoError(t, err)
+	require.Equal(t, []Video{{Name: "video2"}}, res)
+
+	// Force delete only soft deleted videos.
+	_, err = db.NewDelete().Model((*Video)(nil)).WhereDeleted().ForceDelete().Exec(ctx)
+	require.NoError(t, err)
+
+	// Check one remaining video.
+	err = db.NewSelect().Model((*Video)(nil)).Column("name").WhereAllWithDeleted().Scan(ctx, &res)
+	require.NoError(t, err)
+	require.Equal(t, []Video{{Name: "video3"}}, res)
+
+	// Force delete all videos.
+	_, err = db.NewDelete().Model((*Video)(nil)).Where("1 = 1").ForceDelete().Exec(ctx)
 	require.NoError(t, err)
 
+	// Check no remaining videos.
 	count, err := db.NewSelect().Model((*Video)(nil)).WhereAllWithDeleted().Count(ctx)
 	require.NoError(t, err)
 	require.Equal(t, 0, count)

query_base.go

@@ -237,7 +237,7 @@ func (q *baseQuery) isSoftDelete() bool {
 	if q.table != nil {
 		return q.table.SoftDeleteField != nil &&
 			!q.flags.Has(allWithDeletedFlag) &&
-			!q.flags.Has(forceDeleteFlag)
+			(!q.flags.Has(forceDeleteFlag) || q.flags.Has(deletedFlag))
 	}
 	return false
 }
@@ -767,7 +767,7 @@ func (q *whereBaseQuery) addWhereCols(cols []string) {
 func (q *whereBaseQuery) mustAppendWhere(
 	fmter schema.Formatter, b []byte, withAlias bool,
 ) ([]byte, error) {
-	if len(q.where) == 0 && q.whereFields == nil {
+	if len(q.where) == 0 && q.whereFields == nil && !q.flags.Has(deletedFlag) {
 		err := errors.New("bun: Update and Delete queries require at least one Where")
 		return nil, err
 	}

query_delete.go

@@ -158,7 +158,6 @@ func (q *DeleteQuery) AppendQuery(fmter schema.Formatter, b []byte) (_ []byte, e
 		return upd.AppendQuery(fmter, b)
 	}
 
-	q = q.WhereDeleted()
 	withAlias := q.db.features.Has(feature.DeleteTableAlias)
 
 	b, err = q.appendWith(fmter, b)