Support for EnvelopeWithTimePeriod in Coverage Descriptions

[bpross-52n]

Is your feature request related to a problem? Please describe.
Some tests already check whether a Coverage Description contains an Envelope or EnvelopeWithTimePeriod (see here). This should be extended to other tests that currently expect an Envelope and thus can create incorrect requests. See #124

Describe the solution you'd like
Tests should check whether an Envelope or EnvelopeWithTimePeriod exist and create requests accordingly.