DEVX-6810: Add support for E2EE

[superchilled]

Description

This PR does the following:

• Updates the Opentok#create_session method to:

  • Add an option for :e2ee to valid_opts
  • Adds conditional checks to the method ensure :e2ee is not set to true if :media_mode is :relayed or if :archive_mode is :always
  • Update the docs comments to provide information on the new param and a link to the relevant OpenTok documentation

• Adds unit tests for the new functionality described above

Motivation and Context

It implements a feature in the SDK which is being added to the API.

How Has This Been Tested?

Added a number tests for calling Opentok#create_session with the new :e2ee param set, as well as tests for invalid configuration options

Example Output or Screenshots (if appropriate):

n/a

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:

• 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.

[jeffswartz]

Should we rev the version to 4.6.0 in the version.rb file? And note changes in the CHANGES.md file?

[jeffswartz]

Please add a commit to rev the minor version.