Better error message for incompatible call metadata

[ascjones]

User reported an error with what looks like an incompatible call, for which we receive the following generic error message:

Node metadata is not fully compatible

From this error variant:

subxt/subxt/src/metadata/metadata_type.rs

Line 81 in e3732e3

IncompatibleMetadata,

, raised here

subxt/codegen/src/api/calls.rs

Line 149 in 0d67b80

Err(::subxt::MetadataError::IncompatibleMetadata.into())

.

What would be better is something with more context e.g:

Metadata for the "instantiate" call is incompatible with the target node or similar.

Possibly we already discussed this issue in the original PR but I can't find anything to link to.

[jsdw]

I popped this in the next release milestone; seems like a small ergonomic win that would be good to get in!

In theory, it should be obvious from the code what call didn't work, so I think this is more useful for us when users report things then actually for users themselves.