feat(firestore): Support BSON types

firestore/bson_types.go

@@ -0,0 +1,53 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package firestore
+
+// BSONObjectID represents a BSON ObjectID as a 24-character lowercase hex string.
+type BSONObjectID string
+
+// String returns the string representation of the BSONObjectID.
+func (id BSONObjectID) String() string {
+	return string(id)
+}
+
+// BSONRegex represents a BSON Regular Expression.
+type BSONRegex struct {
+	Pattern string
+	Options string
+}
+
+// BSONTimestamp represents a BSON Timestamp.
+type BSONTimestamp struct {
+	Seconds   uint32
+	Increment uint32
+}
+
+// BSONDecimal128 represents a BSON Decimal128.
+type BSONDecimal128 string
+
+// BSONMinKey represents BSON MinKey.
+type BSONMinKey struct{}
+
+// BSONMaxKey represents BSON MaxKey.
+type BSONMaxKey struct{}
+
+// BSONBinary represents BSON Binary data with subtype != 0.
+type BSONBinary struct {
+	Subtype byte
+	Data    []byte
+}
+
+// BSONInt32 represents a BSON 32-bit integer.
+type BSONInt32 int32