curl --location --request POST '/auth/signup' \
--header 'Content-Type: application/json' \
--data-raw '{
"language": "ja"
}'
{
"id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
"githubUserId": 1,
"githubUsername": "string",
"githubDisplayName": "string",
"email": "user@example.com",
"avatarUrl": "string",
"language": "ja",
"createdAt": "2019-08-24T14:15:22Z",
"updatedAt": "2019-08-24T14:15:22Z"
}