feat(connectors): web service endpoint decorator

Is your feature request related to a problem? Please describe.

When developing new method, I don't like brainless copy-pasting of connector web-service file and manual initiating it in connector getOrCreateWebServices().
Most (all?) endpoints simply link specific connector method to open-api path, sometimes restricting access roles.
In the end: error prone, no code reuse, many endpoints differ slightly but should behave the same (error handling, logging, etc...)

Describe the solution you'd like

I'd like to simplify the process of defining endpoints by use of decorators (ECMAScript ones from TS5, not experimental).

Example

    @WebService({
        httpVerb: "post", // possibly enum
        path: "/api/v1/plugins/@hyperledger/cactus-plugin-ledger-connector-ethereum/deploy-contract",  
    })
    @WebServiceAccess(roles)
    public async deployContract(
        req: DeployContractV1Request,
    ): Promise<RunTransactionResponse> {
        // ...
    }

This would create new IWebServiceEndpoint and add it to decorated method class field this.endpoints (that can later be used by cmd-api-server to create an actual endpoint).

More benefits:

Decorator can be used to register these methods as websocket / grpc endpoints in the future as well.
@WebServiceAccess can be used to define common access control across protocols (e.g. websockets doesn't limit access at the moment).
Simplified implementation of new connector, no need to jump around files to see what methods are exported through web services.

Describe alternatives you've considered

Factory method for creating IWebServiceEndpoint with default structure (reused by most endpoints).
TS experimental decorators before (but new ones are better alternative).

Additional context

@petermetz @takeutak @izuru0 @jagpreetsinghsasan @VRamakrishna @sandeepnRES This is just a generic idea, please let me know what you think and then I can work on PoC to make sure it works as expected.

hyperledger-cacti / cacti

feat(connectors): web service endpoint decorator #2974