Cache-Control Header max-age=0 is Implicit in no-store

[jscottbranson]

The rfcs require the 'Cache-Control' response header be set to 'max-age=0', however, it appears to be more appropriate to use the 'no-store' directive, as it is more broad in that it assumes 'max-age=0' as well as 'must-revalidate'.

Credit to @RareData for talking through which headers are appropriate with me. Markus also observed that the 'no-transform' directive might be appropriate.

Also credit to @XRPL-Labs, whose PayID implementation first alerted me to the 'no-store' directive.

[aanchal4]

Thanks @CrypticRabbit for bringing this up. Sounds reasonable to me! Will update the RFC in next iteration.

[jscottbranson]

Just circling back to this, thanks for merging.