fix ContractXDR encoding

• fixes the encoding of a SCValXDR of type void. Resolves issue #160

Protocol 21 Support

adds support for protocol 21. see #159

SEP-08 support

• add SEP-08 Support (Regulated Assets). See doc
• remove UserDefaults usage in SEP-07. See #158
• update Soroban RPC args for sendTransaction and getTransaction

Update SEP-06 Support

update SEP-06 to reflect current SEP-06 doc version. See also: SDK doc.

SEP-38 (Anchor RFQ API) Support

• Add support for SEP-38 - Anchor RFQ API. See example

Optional transaction meta

• allow optional transaction meta in horizon transaction response
• see: https://discord.com/channels/897514728459468821/900374272751591424/1199438109796999298

Sep-009 update

• update and extend SEP-09 kyc fields

Soroban & SEP-006 Improvements

• extend soroban send transaction response (see #156)
• improve sep-006 support: add amount_in_asset and amount_out_asset anchor transaction response fields

Soroban 20.0.2 support

• add support for soroban 20.0.2
• this release contains breaking changes, see also #154

SEP-30 Support

• Add support for SEP-30. See example
• Rename expirationLedgerSeq from soroban rpc response