feat(REST URL): removing default REST URL anti-pattern. Error thrown if URL is not specified at startup

package.json

@@ -10,7 +10,7 @@
   ],
   "main": "src/bch-js.js",
   "scripts": {
-    "test": "c8 mocha --trace-warnings --unhandled-rejections=strict --timeout 30000 test/unit/",
+    "test": "export RESTURL=http://localhost:5942/v6/ && c8 mocha --trace-warnings --unhandled-rejections=strict --timeout 30000 test/unit/",
     "test:integration": "npm run test:integration:local:noauth",
     "test:integration:nft": "export RESTURL=https://bchn.fullstack.cash/v6/ && export IS_USING_FREE_TIER=true && mocha --timeout 30000 -g '#nft1' test/integration/slp.js",
     "test:integration:bchn": "export RESTURL=https://bchn.fullstack.cash/v6/ && export IS_USING_FREE_TIER=true && mocha --timeout 30000 test/integration/",

src/bch-js.js

@@ -45,7 +45,6 @@ import Ecash from './ecash.js'
 // Indexers
 import Electrumx from './electrumx.js'
 import PsfSlpIndexer from './psf-slp-indexer.js'
-const DEFAULT_REST_API = 'https://api.fullstack.cash/v6/'
 
 class BCHJS {
   constructor (config) {
@@ -54,7 +53,11 @@ class BCHJS {
       this.restURL = config.restURL
     } else if (process.env.RESTURL && process.env.RESTURL !== '') {
       this.restURL = process.env.RESTURL
-    } else this.restURL = DEFAULT_REST_API
+    } else {
+      throw new Error(
+        'REST API URL is required. Provide config.restURL or set the RESTURL environment variable.'
+      )
+    }
 
     // Retrieve the Bearer token for simple token authentication.
     this.bearerToken = '' // default value.

src/electrumx.js

@@ -534,6 +534,8 @@ class ElectrumX {
    */
   async txData (txid) {
     try {
+      console.log('bch-js txData() restURL: ', this.restURL)
+
       // Handle single transaction.
       if (typeof txid === 'string') {
         const response = await this.axios.get(