refactor out some panics in CedarProto

[cdisselkoen]

Refactors out some panics in CedarProto. Specifically, the Protobuf parser now gracefully fails (rather than panicking) when encountering:

• unknown extension type (in a schema)
• ip() or decimal() argument that fails to parse
• expression of an unsupported variant (ie not a restricted expression) where a Value is expected

[shaobo-he-aws]

Nit: I'm uncertain if we need this function here. Intuitively,

let attrs ← attrs.toList.mapM λ (k,v) => do
    let v ← v.map ProtoType.toCedarType |>.transpose
    .ok (k, v)

can be written like

let attrs ← attrs.toList.mapM λ (k,q) => do
    let t ← ProtoType.toCedarType q.getType
    .ok (k, q.map ∘ Function.const t)

Or we can write this function as q.getType.map fun t1 => q.map ∘ Function.const t1

[shaobo-he-aws]

Syntactically correct version:

def transpose {α ε} (q : Qualified (Except ε α)) : Except ε (Qualified α) :=
  q.getType.map ((q.map ∘ Function.const _) ·)

[cdisselkoen]

I acknowledge you're correct, but I find that harder to read; anyone else have thoughts?

[adpaco-aws]

The current definition seems more readable to me. I don't know what q.getType or Function.const mean so I guess some familiarity with those methods is needed.

[shaobo-he-aws]

LGTM

[adpaco-aws]

The current definition seems more readable to me. I don't know what q.getType or Function.const mean so I guess some familiarity with those methods is needed.