fix: withdraw/deposit converts from BZZ (10^16 base units) (#66)

* refactor: added toBZZbaseUnit function

* feat: added utility for attesting value is BZZ convertible to base units

* fix: conversion from 15 to 16 decimal places, added unsafe versions

* refactor: withdraw modal uses the safe conversion from BZZ

* refactor: added BigNumber and Token class to handle BZZ digits correctly

* refactor: extract deposit and withdraw functionality into single modal

* test: added tests for Token

* chore: removed unused component

* chore: addressed PR review, token decimal is now integer 0-18

* chore: added comment to clarify the value restriction on token amount

package-lock.json

@@ -15,6 +15,7 @@
         "@types/react-router": "^5.1.13",
         "@types/react-router-dom": "^5.1.7",
         "axios": "^0.21.1",
+        "bignumber.js": "^9.0.1",
         "feather-icons": "^4.28.0",
         "material-ui-dropzone": "^3.5.0",
         "qrcode.react": "^1.0.1",
@@ -4252,6 +4253,14 @@
         "node": "*"
       }
     },
+    "node_modules/bignumber.js": {
+      "version": "9.0.1",
+      "resolved": "https://registry.npmjs.org/bignumber.js/-/bignumber.js-9.0.1.tgz",
+      "integrity": "sha512-IdZR9mh6ahOBv/hYGiXyVuyCetmGJhtYkqLBpTStdhEGjegpPlUawydyaF3pbIOFynJTpllEs+NP+CS9jKFLjA==",
+      "engines": {
+        "node": "*"
+      }
+    },
     "node_modules/binary-extensions": {
       "version": "2.2.0",
       "resolved": "https://registry.npmjs.org/binary-extensions/-/binary-extensions-2.2.0.tgz",
@@ -25127,6 +25136,11 @@
       "integrity": "sha512-vyL2OymJxmarO8gxMr0mhChsO9QGwhynfuu4+MHTAW6czfq9humCB7rKpUjDd9YUiDPU4mzpyupFSvOClAwbmQ==",
       "dev": true
     },
+    "bignumber.js": {
+      "version": "9.0.1",
+      "resolved": "https://registry.npmjs.org/bignumber.js/-/bignumber.js-9.0.1.tgz",
+      "integrity": "sha512-IdZR9mh6ahOBv/hYGiXyVuyCetmGJhtYkqLBpTStdhEGjegpPlUawydyaF3pbIOFynJTpllEs+NP+CS9jKFLjA=="
+    },
     "binary-extensions": {
       "version": "2.2.0",
       "resolved": "https://registry.npmjs.org/binary-extensions/-/binary-extensions-2.2.0.tgz",