use non-static strings errors

[PiRK]

This enables uses cases that require error message built with runtime data such as

RPCError::InvalidParamsString(format!("Method {method_name} requires {num_required} params, got {num_actual}"))

// Forward error message
RPCError::CustomErrorString(1, err.what().to_string())

Here is an example of a use case:

https://reviews.bitcoinabc.org/D17427
In this example the server needs to forward the exact same error message returned by a backend bitcoin node when attempting to broadcast a transaction, so that clients can troubleshoot issues with transaction building.

[PiRK]

I added new error types rather than changing the existing ones, to avoid breaking code for your other users. But I'm also happy with just changing the string type for the existing CustomError and InvalidParams if you prefer, and adjust the rest of my code accordingly.

I'm also open to suggestions for better names for these two new errors.

[hozan23]

Hello @PiRK,

Thank you for the PR. Could you please remove the ones with &str and use String instead? One of them is probably enough.

Something like:

#[error("Custom Error:  code: {0} msg: {1}")]
CustomError(i32, String),

#[error("Invalid Params: {0}")]
InvalidParams(String),

[hozan23]

Since you're already working on it, could you please change the other error types to use String instead of &'static str? I don't remember exactly why I chose &str instead of just String.

Thank you

[hozan23]

I added new error types rather than changing the existing ones, to avoid breaking code for your other users. But I'm also happy with just changing the string type for the existing CustomError and InvalidParams if you prefer, and adjust the rest of my code accordingly.

I'm also open to suggestions for better names for these two new errors.

I think it would be much cleaner to change the existing ones. Thanks.

[PiRK]

I split the changes into two commits, one for RPCError (which does not require other changes in the codebase) and another one for other error types.