v0.3

• Changed OpenID4VP response mode from direct_post to direct_post.jwt as it is required following the current HAIP specs.
• Introduced psp claim holding a PSP Identifier as URI.
• Introduced PSP metadata. Using the identifier given in the PSP claim, a TPP can retrieve the required technical information it needs to process a payment. Therefor these information (payment_uri, payment_status_uri or msct_uri e.g.) don't need to be included in the A2Pay anymore and can be updated withour reissuing the A2Pay.
• Removed payment_uri, currency and msct_uri from A2Pay.
• Removed the payment_status_uri from the direct_post and a2pay-direct responses.
• Remarks on status polling behaviour.