Limitations of CIR to resolve certain CAS numbers

[jonwzheng]

Issue

Sometimes the CIR is unable to resolve CAS numbers. This may limit the use of the RMG website if a user is unable to find the adjacency list using CAS number as a search.

Reproduce this

Go to the RMG molecule search (https://rmg.mit.edu/molecule_search) and search for 16940-81-1. You will see that the CIR is unable to resolve the CAS number, but if you instead search on CAS Common Chemistry (https://commonchemistry.cas.org/results?q=16940-81-1) the CAS number can be found.

Proposed fix / Todo

Implement a screener that detects whether the user input is in the form of a CAS number, and if so, search using the CAS Common Chemistry API instead of CIR.