GraphQLIT - Improve code quality and provide separation of concerns.

[etugarev]

Improved test & README

Customer IT tests run after the product tests are run and suppose to test customer's added functionality.

Removed tests

• testQueryWithSyntaxError
• testQueryWithErrorResponse

Those tests were testing aemHeadlessClient itself (ability to throw an AEMHeadlessClientException), which should be part of product tests and not a customer IT tests.

Fixed potential NPE

• testListPersistedQueries

Updated README.md:

Test GraphQLEndpointITrequred publish instance up and running and having persisted query published, updated documentation to reflect this.

Styling

Test GraphQlIT renamed to GraphQLIT, to as L stands for "Language", which is also a part of "GraphQL" abbreviation.

Related Issue

Motivation and Context

Improve code quality and provide separation of concerns.

How Has This Been Tested?

Locally and on cloud environment

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.