How to use Security and SecurityRequirement

[SOHELAHMED7]

Fixes #75

---

Current issues:

            'paths' => [
                '/test' => new PathItem([
                    'get' => new Operation([
                        'security' => [new SecurityRequirement(['BearerAuth' => []])],
                    ])
                ])
            ]

yields

'paths' => Array &1 (
        '/test' => Array &2 (
            'get' => Array &3 (
                'security' => Array &4 (
                    0 => Array &5 (
                        'BearerAuth' => Array &6 ()
                    )
                )
            )
        )
    )

---

            'paths' => [
                '/test' => new PathItem([
                    'get' => new Operation([
                        'security' => [new SecurityRequirement(['BearerAuth'])],
                    ])
                ])
            ]

yields

'paths' => Array &1 (
        '/test' => Array &2 (
            'get' => Array &3 (
                'security' => Array &4 (
                    0 => Array &5 (
                        0 => 'BearerAuth'
                    )
                )
            )
        )
    )

---

            'paths' => [
                '/test' => new PathItem([
                    'get' => new Operation([
                        'security' => [
                            'BearerAuth' => new SecurityRequirement([])
                        ],
                    ])
                ])
            ]

yields

'paths' => Array &1 (
        '/test' => Array &2 (
            'get' => Array &3 (
                'security' => Array &4 (
                    0 => Array &5 ()
                )
            )
        )
    )

This PR fixes above issues as

            'paths' => [
                '/test' => new PathItem([
                    'get' => new Operation([
                        'security' => new SecurityRequirements([
                            'BearerAuth' => new SecurityRequirement([])
                        ]),
                    ])
                ])
            ]

yields

'paths' => Array &1 (
        '/test' => Array &2 (
            'get' => Array &3 (
                'security' => Array &4 (
                    'BearerAuth' => Array &5 ( )
                )
            )
        )
    )