Support High-level API for GraphQL

[heowc]

Currently, armeria-graphql is based on graphql-java and provides a very low-level API. Many frameworks or libraries provide high-level APIs. One of them is that if we create an object such as a simple resolver without creating a data fetcher ourselves, it is naturally connected to the schema.

For example, there are frameworks such as:

• dgs-framework
• spring-graphql
• graphql-java-kickstart

It is still unclear how to solve this, but I think it is necessary for user convenience. 🤔