feature/665 - Add NoSecurity decorator

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Resolves feature request #665 by adding a NoSecurity decorator that can be used to override the Security decorator on a class.

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Potential Problems With The Approach

The noSecurityDecorators variable name could be seen as a little ambiguous, but is not publicly visible.

Test plan

Tests will be added once the maintainers are happy with my approach in the PR (and I get to grips with these unit tests). Ones I can think of are:

• MethodGenerator.getSecurity returns empty array when NoSecurity decorator is used.

I can't seem to find any way of testing invalid decorator usage, but have verified that the following errors are thrown as expected.

• ControllerGenerator.getSecurity throws when a NoSecurity decorator is used.
• MethodGenerator.getSecurity throws when multiple NoSecurity decorators are used.
• MethodGenerator.getSecurity throws when NoSecurity and Security decorators are used.

[WoH]

LGTM, thanks a lot!