Add contract invoke helper to ConcordiumProvider

[Bargsteen]

Description
The Concordium provider that you get from detectConcordiumProvider has a nice interface for contract init and update where it automatically serializes the parameters using a provided schema. But when you want to invoke a contract, you have to go down one level of abstraction and use jsonRpcClient.

It would be great if we could add a helper method for invoking contracts at the same level of abstraction as init and update.

Current

With contract updates, we can provide a JSON parameter and a module schema as a string

 client
.sendTransaction(
    currentAccountAddress,
    concordiumSDK.AccountTransactionType.Update,
    {
        amount: new concordiumSDK.CcdAmount(0n),
        contractAddress: {
            index: contractIndex,
            subindex: 0n,
        },
        receiveName: 'voting.vote',
        maxContractExecutionEnergy: 3000n,
    },
    votingOption,
    rawModuleSchema,
)
.then((msg) => alert(`Successfully sent vote with transaction hash: "${msg}"`))
.catch(alert);

But for invocations, you have to use the json rpc client directly, which is at a lower level of abstraction.

Here, you have to serialize the parameter and deserialize the return value manually.
You also have to specify contract and entrypoint as two separate parameters, instead of a receive name (<contract_name>.<entrypoint_name>).

const inputParams = serializeUpdateContractParameters("voting.view", { my: "JSON parameter"}, rawModuleSchema);

client.getJsonRpcClient().invokeContract({ // Using json rpc client
    contract: { index: BigInt(contractIndex), subindex: BigInt(0) },
    method: 'voting.view',
    parameter: inputParams
})
.then((viewResult) => {
    let returnValue = concordiumSDK.deserializeReceiveReturnValue(
        concordiumSDK.toBuffer(viewResult.returnValue, 'hex'),
        concordiumSDK.toBuffer(rawModuleSchema, 'base64'),
        "voting",
        "view", // NOTE: Here it is just the entrypoint name, i.e. the contract name is not prepended.
        concordiumSDK.SchemaVersion.V2
    );
})
.catch(alert);

Suggestion

client.invokeContract({                  //  <-- Helper function directly on client
    contract: { index: BigInt(contractIndex), subindex: BigInt(0) },
    method: 'voting.view',
    parameter: { my: "JSON parameter" }, // <-- Directly provide json schema
    rawModuleSchema                      // <-- And schema
})
.then((viewResult) => {
    // The viewResult is the deserialized return value.
    let field_a = viewResult.a;
})
.catch(alert);

[abizjak]

Can I add to this that it would also be nice to expose CIS2 functionality for querying balance and metadata directly. Like the cis2Client we have in the Rust SDK.