Fix complex query param validation

[kunalrkak]

Before this PR

Conjure endpoint validator allows nested containers in an endpoint query argument, for example:

ArgumentDefinition:
    type: optional<list<string>>
    param-type: query

Query params cannot be nested container types, as container inner types must be serialized using PLAIN format, which only supports primitives + enums.

The example above in particular creates ambiguity in the wire format (since types with multiple elements are encoded to urls as a series of individual elements: ?arg=foo,arg=bar, while optional types are simply omitted from the query string if the value is not present [docs]). In this case, an absence of the argument could be either the empty optional or a present optional with an empty list.

After this PR

==COMMIT_MSG==
Conjure endpoint validator throws for nested container query arguments.
==COMMIT_MSG==

Possible downsides?

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Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

Conjure endpoint validator throws for nested container query arguments.

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[carterkozak]

I think the clearest existing docs which support this are from ArgumentDefinition:

If the param-type is query then the de-aliased type MUST be an enum or a primitive (except binary and bearertoken), or a container (list, set, optional) of one of these

[mpritham]

Shall we add a test for container<enum> to exercise the case where we recurse and the de-aliasing visitor returns Either.left?

[kunalrkak]

good call, will add!