ValidateBlobNamespace: cleaning up and future-proofing

[ivan-gavran]

There seems to be some confusion about blob namespace validation:

• there are two functions called ValidateBlobNamespace: one (A) is a member function of the Namespace structure, and the other (B) takes Namespace as an argument. The two functions are almost identical, the only difference being that B checks if the namespace version is NamespaceVersionZero.
• Interestingly, both functions are used in a similar context: A is called from within ValidateBlobTx (which is called both from ProcessProposal and CheckTx). B is called from within ValidateBasic of MsgPayForBlobs, which is also called from ValidateBlobTx.
• My guess is that calling both of these functions is unnecessary and that B should be the used one.

Finally, a question of future-proving: would it make sense to replace the explicit check for version 0,

if ns.Version != appns.NamespaceVersionZero {
		return ErrInvalidNamespaceVersion
	}

with a check for whether the ns.Version is among the supported user-namespace versions? (Along the lines of how it was done for share versions, here.)

There is another function which validates namespace versions, ValidateVersion. In this validation, both zero-namespace and max-namespace are allowed (so, it is checking for any possible versions, and not just user-created blobs). It would probably make sense to change the name of that function into something more concrete, e.g., ValidateVersionSupported.

relevant commit: v1.0.0-rc6