New test cases for SLP txDetails() and validateTxid()

[christroutner]

A Schnorr-signature-based transaction is producing errors in the latest version of the stage branch in rest. This issue captures the error codes and URLs being tested on stage. The scope of work to solve this issue includes updates to these two endpoints to handle this use case, and to add unit tests that capture this use case.

TXID: d7183ddef6acea521c526c30b97101d36a9e96a2e411e2721b22033ba07b72e1

validateTxid()

https://rest.btctest.net/v2/slp/validateTxid/d7183ddef6acea521c526c30b97101d36a9e96a2e411e2721b22033ba07b72e1

Produces this error:

{
  "error": "TypeError: Cannot read property 'valid' of undefined\n    at /var/www/rest.bitcoin.com/dist/routes/v2/slp.js:1334:55\n    at step (/var/www/rest.bitcoin.com/dist/routes/v2/slp.js:43:23)\n    at Object.next (/var/www/rest.bitcoin.com/dist/routes/v2/slp.js:24:53)\n    at fulfilled (/var/www/rest.bitcoin.com/dist/routes/v2/slp.js:15:58)\n    at process._tickCallback (internal/process/next_tick.js:68:7)"
}

txDetails()

https://rest.btctest.net/v2/slp/txDetails/https://rest.btctest.net/v2/slp/validateTxid/d7183ddef6acea521c526c30b97101d36a9e96a2e411e2721b22033ba07b72e1

Produces this error:

{
  "status": 404,
  "message": "Not Found"
}