feature/customEmailProvider

[tusharpandey13]

This PR adds support for the custom email provider

Changes

• SDK-5186 update api for custom email provider support
• fix tests for email provider

Copy of #1065, builds on work already done by @acwest

References

https://auth0.com/docs/api/management/v2/emails/post-provider

Tests

PASSING

Test Suites: 45 passed, 45 total
Tests:       1447 passed, 1447 total
Snapshots:   0 total
Time:        7.402 s, estimated 9 s
Ran all test suites.

Sample code / manual testing

import { EmailProviderCreate } from 'auth0';

const data: EmailProviderCreate = {
  name: 'custom',
  enabled: true,
  default_from_address: 'string',
  credentials: {},
  settings: {}
};

managementClient.emails.configure(data)
  .then(response => {
    console.log('Email provider configured successfully:', response);
  })
  .catch(error => {
    console.error('Error configuring email provider:', error);
  });