add neynar connection

curl --request POST \
  --url https://api-staging.boost.xyz/users/neynar \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "signerId": "<string>"
}'

{
  "userId": "<string>",
  "fid": 123,
  "username": "<string>",
  "displayName": "<string>",
  "profileImageUrl": "<string>"
}