services/user relies on config.AUTH0.DOMAIN config param being available; if there is no AUTH0 segment in the config, the code crush; thus preventing the library to work even when host code does not need related functionality.

We should update auth0-js initialization to be lazy.

Replacing direct API calls to get m2m token with the library (tc-core-library-js)

I guess, it can be droped in favor of a function from lodash?

Describe the bug
The API returns an Unable to process JSON error when the user tries to change the email address from the Settings page

To Reproduce
Steps to reproduce the behavior:

1. Go to https://www.topcoder.com/settings/account
2. Click on Change email
3. Enter the new email and click Send verification email
4. See error

Expected behavior
Only the required properties for changing the email should be passed in the request body to prevent such errors from unused properties.

This #30 PR introduced code quality issues that should be fixed.

Most of them are in https://github.com/topcoder-platform/topcoder-react-lib/blob/1e4b154636c86c111b964c0258e6a6706735cf1a/src/services/challenges.js but everything should be checked and fixed.

• Fix eslint issues and revert rules to the default configs
• Fix many typos v3 => v4 in method documentation.
• We use the getApiResponsePayloadV3() method with the response from the V4.
• getApiV3 is defined but never used.
• We defined both this.private.api and this.private.apiV4 as getApiV4(tokenV3). This is confusing.

1. I think this whole thing can be rewritten using API factory function. And usage will be like

const { getApi } = services.api;
const api = getApi(version='V4',tokenV3)

This might need change on the community app side but it will generic for next versions.

2. I think we should remove every mention of v4 from the docs, there are many places where there is v4. Probably in a month or two, we will be launching v5
   https://github.com/topcoder-platform/topcoder-react-lib/pull/33/files search for v4