tx.fhir.org only appears to be loading the latest version of packages

[brynrhodes]

3. Missing us core value set: http://hl7.org/fhir/us/core/ValueSet/us-core-vital-signs|6.1.0
   1. Value set is in the parameters correctly
   2. Value set is in the dependencies correctly
   3. Value set is correctly listed as "not in the repository" (because yeah, it's not, because tx.fhir.org appears to only be loading the latest versions)

[brynrhodes]

Confirmed, there is no guarantee that the contents of any particular package will be available in tx.fhir.org. It looks like maybe the latest versions of packages are there, but it's likely that even that isn't a guarantee, so we need to be more defensive about this, and hand the server content that it needs using the txResource parameter. See the Zulip thread here:

https://chat.fhir.org/#narrow/channel/179202-terminology/topic/Prior.20versions.20of.20value.20sets.20in.20tx.2Efhir.2Eorg.3F/with/613696667

Basically, we get the definitions from NPM already, so just hand those to the txServer if the server doesn't have the value set already.