feat: added v3 proto for online/batch document translation and updated v3beta1 proto for format conversion

protos/google/cloud/translate/v3beta1/translation_service.proto

@@ -22,6 +22,7 @@ import "google/api/field_behavior.proto";
 import "google/api/resource.proto";
 import "google/longrunning/operations.proto";
 import "google/protobuf/timestamp.proto";
+import "google/rpc/status.proto";
 
 option cc_enable_arenas = true;
 option csharp_namespace = "Google.Cloud.Translate.V3Beta1";
@@ -1241,6 +1242,19 @@ message BatchTranslateDocumentRequest {
   // Optional. Glossaries to be applied. It's keyed by target language code.
   map<string, TranslateTextGlossaryConfig> glossaries = 7
       [(google.api.field_behavior) = OPTIONAL];
+
+  // Optional. File format conversion map to be applied to all input files.
+  // Map's key is the original mime_type. Map's value is the target mime_type of
+  // translated documents.
+  //
+  // Supported file format conversion includes:
+  // - `application/pdf` to
+  //   `application/vnd.openxmlformats-officedocument.wordprocessingml.document`
+  //
+  // If nothing specified, output files will be in the same format as the
+  // original file.
+  map<string, string> format_conversions = 8
+      [(google.api.field_behavior) = OPTIONAL];
 }
 
 // Input configuration for BatchTranslateDocument request.