.appRoleLogin() requires secret_id, which can be an optional field

[ryanlewis]

According to the Vault docs for logging in with AppRole, it appears that the secret_id is not always required if bind_secret_id=false against the AppRole.

However, we get the following error: Missing required property: secret_id.

Repro code:

const NodeVault = require("node-vault");

const vault = NodeVault({ apiVersion: "v1", endpoint: process.env.VAULT_URL });

vault
  .approleLogin({ role_id: 'ebadc783-4b12-e465-3f84-3490d297c88d', requestOptions: { followAllRedirects: true } })
  .then(result => console.log(result))
  .catch(err => console.error(err));

This produces the following output:

{ Error
    at new ValidationError (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:1461:12)
    at ValidatorContext.createError (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:359:14)
    at ValidatorContext.validateObjectRequiredProperties (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:993:22)
    at ValidatorContext.validateObject (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:960:11)
    at ValidatorContext.validateAll (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:603:11)
    at Object.validate (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:1573:24)
    at validate (/Users/rlew/Desktop/node-vault-repro/node_modules/node-vault/src/index.js:138:23)
    at Object.client.(anonymous function) [as approleLogin] (/Users/rlew/Desktop/node-vault-repro/node_modules/node-vault/src/index.js:172:14)
    at Object.<anonymous> (/Users/rlew/Desktop/node-vault-repro/node-vault-repro.js:6:4)
    at Module._compile (module.js:635:30)
  message: 'Missing required property: secret_id',
  params: { key: 'secret_id' },
  code: 302,
  dataPath: '',
  schemaPath: '/required/1',
  subErrors: null,
  stack: 'Error\n    at new ValidationError (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:1461:12)\n    at ValidatorContext.createError (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:359:14)\n    at ValidatorContext.validateObjectRequiredProperties (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:993:22)\n    at ValidatorContext.validateObject (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:960:11)\n    at ValidatorContext.validateAll (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:603:11)\n    at Object.validate (/Users/rlew/Desktop/node-vault-repro/node_modules/tv4/tv4.js:1573:24)\n    at validate (/Users/rlew/Desktop/node-vault-repro/node_modules/node-vault/src/index.js:138:23)\n    at Object.client.(anonymous function) [as approleLogin] (/Users/rlew/Desktop/node-vault-repro/node_modules/node-vault/src/index.js:172:14)\n    at Object.<anonymous> (/Users/rlew/Desktop/node-vault-repro/node-vault-repro.js:6:4)\n    at Module._compile (module.js:635:30)' }

This means that we are unable to use node-vault with AppRoles that do not require a secret_id using node-vault.

[ryanlewis]

PR to change this: #89