Ability to explicitely specify the location of the schema

[martinbonnin]

Right now, the plugin detect the schema automatically when using the Apollo Gradle plugin.

There are some occurences though where I'm not using the Apollo Gradle plugin or just using operation/schemas that aren't "owned" by the plugin. For an example, writing tests.

In those cases, it would be nice to be able to specify the location of the schema for a given executable document:

extend schema @link(url: "https://specs.apollo.dev/ide/v0.0", import: ["@location"])

# points the IDE to the place where the schema is
extend schema @location(path: "schema.graphqls")

query GetFoo {
  foo
}