generator: panic when parameter is repeated Any portrayed as "type: object"

[noahdietz]

An API with RPC request message google.protobuf.HttpBody without a (google.api.http).body set will end up with its repeated google.protobuf.Any extensions field portrayed in Discovery as a type: array with items type: object and additionalProperties containing type: any. The simpleTypeConvert function isn't handling type: object case so it returns !ok and the resulting usage panics, but it would've handled type: any had the additionalProperties been consulted for that field.

Without considering a change to the Discovery document (which we should probably consult the Discovery generation owner about), our options include:

1. Handling type: object in simpleTypeConvert, potentially in the same way as any, using an interface{}
2. Consult the additionalProperties for potential a type field

See this internal post for my detailed debugging process.

[noahdietz]

In the specific case, the issue with the API is actually due the fact that a repeated Any is used as query parameter. Based on the google.api.http documentation repeated non-primitive fields are prohibited from use as query params. So the case that sparked this issue, we would do well to just improve the error messaging.

We also probably still want to handle the simpleTypeConvert case handling for this instance too though.

[noahdietz]

Fix for handling the "object as query parameter" case been released. This ultimately should've been prevented in API service compilation which is where the real fix will be. Closing this now.