add getInterchain: trace a transaction/block to validator blocks + interchain anchors

New transaction.getInterchain and block.getInterchain call the prime-node
/api/v1/{transaction,block}/{id}/interchain endpoints, returning an
InterchainTrace { blockId, validatorBlocks, interchainTransactions }. Adds
VerificationBlock / InterchainTransaction / InterchainTrace interfaces and
method-existence assertions.

src/transaction.ts

@@ -11,6 +11,7 @@ import {
   TransactionBulkResponse,
   Transaction,
   ListTransactionsResponse,
+  InterchainTrace,
 } from './types';
 
 export class TransactionClient {
@@ -49,6 +50,16 @@ export class TransactionClient {
     return this.client.get<Transaction>(`/api/v1/transaction/${transactionId}`);
   }
 
+  /**
+   * Traces a transaction to the validator (verification) blocks that validated
+   * its prime block and the public-chain interchain anchors those validator
+   * blocks were bundled into. If the transaction is still pending (not yet in a
+   * block) the trace's arrays are empty.
+   */
+  async getInterchain(transactionId: string): Promise<InterchainTrace> {
+    return this.client.get<InterchainTrace>(`/api/v1/transaction/${transactionId}/interchain`);
+  }
+
   /**
    * Lists all transactions
    */