Which/how many unused CIDs SHOULD be provided?

[mirjak]

In section https://quicwg.org/multipath/draft-ietf-quic-multipath.html#name-allocating-consuming-and-re we currently say:

"Endpoints SHOULD issue at least one unused connection ID with unused Path Identifier."

I don't think we can or should require to provide one unused Path ID. Instead this sentence originally intended to say that one unused CID should be provide to enable migration. As such this sentence should say:

"Endpoints SHOULD issue at least one unused connection ID with for each active path."

[mirjak]

Further the text says the following:

When there is not enough unused Path Identifiers, endpoints SHOULD
send MAX_PATHS frame to inform the peer that new Path Identifiers are available.

However, it is fully unclear what "not enough" means. I therefore propose to remove this sentence.

[mirjak]

Continue discussion in #338