Define the FLE2EqualityIndexedValueV2 payload type in the EncryptedBinDataType enum in fle_field_schema.idl. Then, create the class FLE2IndexedEqualityEncryptedValueV2 which implements the parseAndDecrypt() and serialize() methods.

The serialize method shall output the binary string that can be parsed as:

index_key_id (16) || bson_type (1) || SKE.Enc(serverToken, ciphertext) || encrypted_counter_and_tag

where encrypted_counter_and_tag can be further parsed as:

SKE.Enc(FS[ f, 2, v, 1 ], (counter || contentionFactor)) || tag || SKE.Enc(FS[ f, 2, v, 2 ], 0^128)