Take decision on whether / how the nexus-python-sdk checks Nexus API specific constraints

This is feedback provided after a first usage of the nexus-python-sdk and its documentation to perform basic operations in a Nexus V1 deployment.

Regarding propagating specifics from the Nexus API, the following questions were noted:

* Should constraints given by the Nexus API be checked / explicitely stated in the nexus-python-sdk, e.g. should the parameter `org_label` in `nexussdk.organizations.create` be checked to not contain upper case letters or spaces?
* Should terms like `vocab` and `base` be further described in the docstrings of the nexus-python-sdk?