Horizon: Protocol 19 Support

[Shaptic]

Breakdown and Rollout: Horizon & Protocol 19. Refer to stellar/projects#26 for a holistic view on other components of Protocol 19.

Horizon

• services/horizon: Support new CAP-21 account fields #4275
• services/horizon: Support new CAP-21 transaction conditions #4276
• services/horizon: Update txsub queue to account for new CAP-21 preconditions #4283
• Testing:
  • Generating full account extensions added back in Uncomment StateVerifier test that generates account v3 extensions #4304
  • Horizon: Protocol 19 Integration Tests #4305
  • Run our branch on staging to ensure full backwards compatibility

SDKs

• Go:
  • all: Add Protocol 19 XDR and update StrKey to support Signed Payloads #4279
  • txnbuild: Update StrKey implementation to support CAP-40 signed payloads #4278
  • txnbuild: Extend transaction building to allow CAP-21 preconditions #4282
  • protocols/horizon: Update API definitions to conform to Protocol 19 #4285
• Java:
  • Update StrKey implementation to support CAP-40 signed payloads lightsail-network/java-stellar-sdk#410
  • Update StrKey implementation to support CAP-40 signed payloads lightsail-network/java-stellar-sdk#410
  • Java: Extend transaction building to allow CAP-21 preconditions lightsail-network/java-stellar-sdk#411
  • Java: Update API definitions to conform to Protocol 19 lightsail-network/java-stellar-sdk#412
• JavaScript: Protocol 19 Support js-stellar-sdk#763

Use the Protocol 19 label to find all relevant Platform issues / PRs.