PubChem needs API key support

[egonw]

From their blog [0]:

I author software that accesses the E-utilities, and this software is used
by other people. Do those users need keys?

Yes, but only if your software allows them to post more than
3 requests/second. For such cases, we recommend that you allow users
to enter their own API key as a setting in the software.  Please 
contact us if you have questions or for more information on this approach.

@jonalv, can you help me with the user account support?

0.https://ncbiinsights.ncbi.nlm.nih.gov/2017/11/02/new-api-keys-for-the-e-utilities/?campaign=twitter-11022017

[egonw]

Note to self: introduce a 0.3s time out in the call if the user does not use a API key.

[jonalv]

What do you need help with more exactly? Sadly I don't really remember how this stuff worked...

[egonw]

OK, long term.