Support for ContentType Parameter in PS7

[mwpreston]

Description

Added support within the Invoke-RubrikWebRequest cmdlet to support adding the required ContentType parameter when issuing DELETE requests when using PowerShell 7 and above. Added cmdlet Test-PowerShellSeven to check powershell version.

Related Issue

Resolves #853

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• [x] 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:

Go over all the following points, and put an x in all the boxes that apply. If you're unsure about any of these, don't hesitate to ask. We're here to help!

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTION document.
• [x] I have updated the CHANGELOG file accordingly for the version that this merge modifies.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[terjedahle]

Hi Mike Preston! I can see you merged this, do you have a link where i can download the new rubrik-sdk module? Version 9.0.1 ?