Resolves a claimed username to its owning address, or None if it
is unclaimed (or was never valid to begin with).
fn resolve(
env: soroban_sdk::Env,
username: soroban_sdk::String,
) -> OptionClaims username for user. Permanent: once claimed a username can
never be released, changed, or transferred, and each address may
claim only one. username must already be lowercase - the contract
rejects anything else rather than silently normalizing it, so a
caller never claims a different string than what it typed.
fn register(
env: soroban_sdk::Env,
user: soroban_sdk::Address,
username: soroban_sdk::String,
)Returns the username user has claimed, if any.
fn username_of(
env: soroban_sdk::Env,
user: soroban_sdk::Address,
) -> OptionTrue if username is well-formed AND still unclaimed.
fn is_available(env: soroban_sdk::Env, username: soroban_sdk::String) -> bool