Make Sentry plugin

[lorensr]

apollo-server-plugin-sentry npm package, based on this:

https://gist.github.com/nodkz/d14b236d67251d2df5674cb446843732

didEncounterErrors(): https://www.apollographql.com/docs/apollo-server/integrations/plugins/#didencountererrors
receives a GraphQLRequestContext: https://github.com/apollographql/apollo-server/blob/dcbbc34/packages/apollo-server-types/src/index.ts#L61-L92

Sentry docs:
https://github.com/getsentry/sentry-javascript/tree/master/packages/node
http://getsentry.github.io/sentry-javascript/modules/minimal.html#captureevent

Then add to branch 29 and expand Error reporting section

[lorensr]

Create two subsections:

• formatError
• Error plugin

or three with health checks