Optional Auth support

[Nauman]

Requirements

When an optional auth is defined:

• Add None to the list of security schemes on the API overview level.
• Add None to the list of security schemes on the endpoint level.
• Add None to the dropdown in try it. If none is selected, user shouldn't have the option to add any credentials.

[Nauman]

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[Nauman]

Closed in favour of #2394