Custom Google OauthStrategy for Feathersjs 4 with email as primary key

authentication.js

const {
  AuthenticationService,
  JWTStrategy
} = require('@feathersjs/authentication');
const {
  expressOauth,
  OAuthStrategy
} = require('@feathersjs/authentication-oauth');

class AdvancedGoogleStrategy extends OAuthStrategy {
  async getEntityQuery(profile, _params) {
    await super.getEntityQuery(profile, _params);
    return {
      email: profile.email
    };
  }

  async getEntityData(profile, _existingEntity, _params) {
    const baseData = await super.getEntityData(
      profile,
      _existingEntity,
      _params
    );
    
    // Get more fields from profile e.g. name, email, picture, given_name, family_name
    const { name, email } = profile;
    const extendedProfile = Object.assign({}, baseData, {
      name,
      email,
    });

    return extendedProfile;
  }
}

module.exports = app => {
  const authentication = new AuthenticationService(app);

  authentication.register('jwt', new JWTStrategy());

  authentication.register('google', new AdvancedGoogleStrategy());

  app.use('/authentication', authentication);

  app.configure(
    expressOauth({
      linkStrategy: 'google'
    })
  );
};