`stellar ledger entry fetch trustline --asset` rejects valid asset codes that aren't exactly 4 or 12 characters

[leighmcculloch]

What problem does your feature solve?

The stellar ledger entry fetch trustline --asset command rejects valid asset codes that aren't exactly 4 or 12 characters long. For example, PYUSD (5 characters) fails:

$ stellar ledger entry fetch trustline --asset PYUSD:GDQE7IXJ4HUHV6RQHIUPRJSEZE4DRS5WY577O2FY6YQ5LVWZ7JZTU2V5 --account GBEPTCX3INOO7565JDEFNCGMKQVTUIWDB356BASWME74RDJOCGQEI7WP
error: provided asset is invalid: PYUSD:GDQE7IXJ4HUHV6RQHIUPRJSEZE4DRS5WY577O2FY6YQ5LVWZ7JZTU2V5

The code matches on the exact length of the asset code string, only accepting lengths 4 and 12:

stellar-cli/cmd/soroban-cli/src/commands/ledger/entry/fetch/trustline.rs

Lines 72 to 80 in a1c9455

	match code.len() {
	4 => TrustLineAsset::CreditAlphanum4(AlphaNum4 {
	asset_code: AssetCode4(code.as_bytes().try_into()?),
	issuer,
	}),
	12 => TrustLineAsset::CreditAlphanum12(AlphaNum12 {
	asset_code: AssetCode12(code.as_bytes().try_into()?),
	issuer,
	}),

Stellar asset codes are 1-4 characters (AssetCode4) or 5-12 characters (AssetCode12), right-padded with zero bytes to fill the fixed-size array.

What would you like to see?

Accept asset codes of any length from 1-12 characters, mapping 1-4 character codes to CreditAlphanum4 and 5-12 character codes to CreditAlphanum12, with the code right-padded with 0 bytes to fill the fixed-size array.

What alternatives are there?

Require users to manually pad their asset codes to 4 or 12 characters, which is not ergonomic and differs from how assets are represented elsewhere in the Stellar ecosystem.