[180] add read/write weights of zero to passthru

[korydraughn]

Does setting these weights to 0.0 block ALL requests on the resource or a specific set of requests?

[trel]

well, no, I think unlink and register and unregister and … might still get through. Rename?

All these would be addressed by adding more verbs to the context string parser (and getting rid of marking things ‘down’… https://github.com/irods/irods/issues/4508)

[trel]

squashed and pushed.