Support strings as power levels under feature = "unstable-synapse-quirks"

[jplatte]

Some older rooms have power level events with string power level rather than integers. To work around this:

• Add an unstable-synapse-quirks feature to ruma-events and forward it from dependent crates

• Create a deserialization function in ruma-serde that accepts both integers and strings

• Add

  #[cfg_attr(feature = "unstable-synapse-quirks", serde(deserialize_with = "ruma_serde::deserialize_int_or_string"))]

  to all power level fields

This still might not handle all existing broken power level events though, since there might also be ones out there that use power levels > MAX_SAFE_INT.

CC @aledomu

[aledomu]

This still might not handle all existing broken power level events though, since there might also be ones out there that use power levels > MAX_SAFE_INT.

That would not be broken, but neglectful. The defacto max power level is 100, we should not prevent anyone in their quest for absolute trouble and destruction by going higher than that.

[jplatte]

No, that would be broken. Canonical JSON, which has to be able to represent any event, explicitly disallows larger values (and values smaller than MIN_SAFE_INT):

Numbers in the JSON must be integers in the range [-(2**53)+1, (2**53)-1].

https://matrix.org/docs/spec/appendices#canonical-json

_{Side note: If that wasn't the case, js_int would not exist}

[aledomu]

I should have phrased it better: it would not be just broken, but even neglectful.