Harmonize: Tests

[lipkau]

The current Test files have different tests, different quality, etc... This should be harmonized.

Ensure all Test files in the module:

• [ ] have a similar quality
  • define a common set of tests for Add-*, Get-*, Invoke-*, Set-*, Remove-*, ConvertTo-*
  • some will not be able to meet the standards of most. Still, a baseline should be created even if some can't meet them
• [ ] have the same syntax
• [ ] have the same structure
  • Context blocks are being used very differently
• [x] use common resources (Shared.ps1) in the same way

[lipkau]

This is a very good start:

• Tests/Remove-JiraIssueAttachment.Tests.ps1
• Tests/Add-JiraIssueAttachment.Tests.ps1