Output correct JSON format when submitting an offline session

[mvandeberg]

Brief description

When submitting an offline transaction, the resulting JSON did not use the correct encodings for binary data. This PR fixes it to do so.

Checklist

• [X] I have built this pull request locally
• [X] I have ran the unit tests locally
• [X] I have manually tested this pull request
• [X] I have reviewed my pull request
• [ ] I have added any relevant tests

Demonstration

Without fix:

🚫 🔓 📄 > session submit
JSON:
{
  "id": "EiCEv74qLN53NG6fo+vJUlhgsK7JCDU7wdKtXwYTV6G4gg==",
  "header": {
    "chain_id": "Zm9vYmFy",
    "rc_limit": 1000000000,
    "nonce": "KBQ=",
    "operation_merkle_root": "EiBHEzzpN+hYlXGwlz6Wg+D9IrJmSPRsVr63tNV2SeYMQQ==",
    "payer": "ACISicKuuJib6PEWx9Zag4wm0wDj3z7sGg=="
  },
  "operations": [
    {
      "Op": {
        "CallContract": {
          "contract_id": "AC4z/RqpB7IkzpzmyUIokB0oOgLalW2nkQ==",
          "entry_point": 670398154,
          "args": "ChkAIhKJwq64mJvo8RbH1lqDjCbTAOPfPuwaEgUF7jPIQxiAlOvcAw=="
        }
      }
    }
  ],
  "signatures": [
    "IKrnZXw/qzbDbCluHMhIYTObDVNsZljkOTOwtrS5I5kyN2ldyzGKkfIlpRCUPDVvTDjzaGwticly6aVTnujOaq0="
  ]
}

Base64:
CiISIIS_vios3nc0bp-j68lSWGCwrskINTvB0q1fBhNXobiCElEKBmZvb2JhchCAlOvcAxoCKBQiIhIgRxM86TfoWJVxsJc-loPg_SKyZkj0bFa-t7TVdknmDEEqGQAiEonCrriYm-jxFsfWWoOMJtMA498-7BoaTRJLChkALjP9GqkHsiTOnObJQiiQHSg6AtqVbaeREMrt1b8CGigKGQAiEonCrriYm-jxFsfWWoOMJtMA498-7BoSBQXuM8hDGICU69wDIkEgqudlfD-rNsNsKW4cyEhhM5sNU2xmWOQ5M7C2tLkjmTI3aV3LMYqR8iWlEJQ8NW9MOPNobC2JyXLppVOe6M5qrQ==

With fix:

🚫 🔓 📄 > session submit
JSON:
{
  "id": "0x122084bfbe2a2cde77346e9fa3ebc9525860b0aec908353bc1d2ad5f061357a1b882",
  "header": {
    "chain_id": "Zm9vYmFy",
    "rc_limit": "1000000000",
    "nonce": "KBQ=",
    "operation_merkle_root": "EiBHEzzpN-hYlXGwlz6Wg-D9IrJmSPRsVr63tNV2SeYMQQ==",
    "payer": "147ABaHVxtpoSpfpZ8yry7eaFAjV87trGR"
  },
  "operations": [
    {
      "call_contract": {
        "contract_id": "15DJN4a8SgrbGhhGksSBASiSYjGnMU8dGL",
        "entry_point": 670398154,
        "args": "ChkAIhKJwq64mJvo8RbH1lqDjCbTAOPfPuwaEgUF7jPIQxiAlOvcAw=="
      }
    }
  ],
  "signatures": [
    "IKrnZXw_qzbDbCluHMhIYTObDVNsZljkOTOwtrS5I5kyN2ldyzGKkfIlpRCUPDVvTDjzaGwticly6aVTnujOaq0="
  ]
}

Base64:
CiISIIS_vios3nc0bp-j68lSWGCwrskINTvB0q1fBhNXobiCElEKBmZvb2JhchCAlOvcAxoCKBQiIhIgRxM86TfoWJVxsJc-loPg_SKyZkj0bFa-t7TVdknmDEEqGQAiEonCrriYm-jxFsfWWoOMJtMA498-7BoaTRJLChkALjP9GqkHsiTOnObJQiiQHSg6AtqVbaeREMrt1b8CGigKGQAiEonCrriYm-jxFsfWWoOMJtMA498-7BoSBQXuM8hDGICU69wDIkEgqudlfD-rNsNsKW4cyEhhM5sNU2xmWOQ5M7C2tLkjmTI3aV3LMYqR8iWlEJQ8NW9MOPNobC2JyXLppVOe6M5qrQ==

Notice the contract ID, transaction ID, contract address, and payer address are all correctly formatted. Furthermore, the base64 encoded fields properly use the URL safe encoding.