patch https://api.fuul.xyz/api/v1/invite_codes/use
Marks an invite code as used and establishes a referral relationship between the user and the code owner. The signature is required to verify ownership of the user identifier.
Required API Key Scope: invite_codes:read
Message to sign: The message must be exactly "I am using invite code {code}" where {code} is replaced with the actual invite code being used.