Option to generate function name based on operationId

[TATSUNO “Taz” Yasuhiro]

Currently, sis automatically generates a function name from path (URL).
It often generates a hard-to-read name if path is complex (has many path parameter).

And even worse, a longer function name may not satisfy limitation (e.g. 64 characters for AWS Lambda), since a Lambda is named by "$service-$stage-$functionName".

It would be helpful if sis generates a function name from operationId in Swagger definition, so function name can be

• human-readable
• short (satisfy Lambda name length)
• stable against API URL change

operationId description

Unique string used to identify the operation. The id MUST be unique among all operations described in the API. The operationId value is case-sensitive. Tools and libraries MAY use the operationId to uniquely identify an operation, therefore, it is RECOMMENDED to follow common programming naming conventions.