Support temporal assertion regarding the absence of gap for a time tick

[Seddryck]

It should be possible to assert that a result-set, with a column for time ticks, is containing/preceding/succeeding a given datetime. A time tick is defined as the closed-open time interval between a datetime and a timespan.

<system-under-test>
  <result-set>
    ...
  </result-set>
</system-under-test>
<assert>
  <without-gap>
    <time-tick start="#3" span="00:15:00"/>
    <over-period start="2022-06-01" end="2022-07-01"/>
    <group-by>...<group-by>
  </without-gap>
</assert>

The optional over-period lets you define that the test should also report failure if the interval covered by the time-ticks is not containing the start and the end of the period. As we're working with closed-open intervals, it's open-end of the time-tick and the open-end of the period should match.

The optional group-by let you define that system-under-test rows should not be tested as a single set of rows but should be subdivided into subsets, each subset being defined by the group-by.