proto: add engine parameter to DDLService.CreateSpace

Part of tarantool/aeon#399

Author: locker

aeon_ddl.proto

@@ -23,6 +23,8 @@ message CreateSpaceRequest {
   repeated FieldDef format = 2;
   // Sorting key definition (indexed fields).
   repeated KeyPartDef key_def = 3;
+  // Storage engine.
+  Engine engine = 4;
 }
 
 message CreateSpaceResponse {

aeon_schema.proto

@@ -31,6 +31,12 @@ message Operation {
   Tuple tuple = 3;
 }
 
+// Storage engine.
+enum Engine {
+  ENGINE_MEMTX = 0;
+  ENGINE_VINYL = 1;
+}
+
 // Type a space field can have.
 enum FieldType {
   FIELD_TYPE_UNSPECIFIED = 0;