Investigate DBS ValidStatus spec parameter and add validation function

[amaltaro]

Impact of the new feature
ReqMgr2 (and WMAgent)

Is your feature request related to a problem? Please describe.
As discussed over the last few days, people are wondering if WMAgent could inject data into DBS with a VALID status (instead of the default PRODUCTION status). This capability would be especially important for the growing Nano workflows.

Describe the solution you'd like
A few actions/deliverables must be done with this ticket:

• first, test whether the StdBase ValidStatus creation parameter is fully functional (i.e., accepting a value provided during creation and propagating it all the way to the agent and DBS3Upload component, ultimately injecting a dataset into DBS with status: VALID).
• if it works, we should add a validation function which will ensure users provide a sound value. List of allowed values should be (PRODUCTION, VALID).

Describe alternatives you've considered
None

Additional context
None