Support Queries with POST-Method

[Jonas Monzel]

Is your feature request related to a problem? Please describe.
Get-requests have a character limit of 2048 character. This is e.g. reached, when filters are build based on earlier requests.
Therefore Kaseya/Autotask states, that POST-Method should be used instead of GET for more complex queries in their API guidelines.

Describe the solution you'd like
Include -Method for Get-AutotaskAPIResource to select between GET and POST request.
To preserve compatibility, this selection must not mandatory.
As POST Request would be need for longer requests only, support for SimpleSearch is not needed.

Describe alternatives you've considered

Additional context
Additionally, this feature detects long requests without this attribute and forces a switch to POST requests.