Create shortcut for BaseService-related imports (#2809)

Continue to implement #2698:

- Add `core/base-service/index.js` (but hold off on moving the things it imports)
- Add shortcuts in `services/index.js` for Base*Service, errors, and deprecatedService. This file will be streamlined later to avoid cluttering it with rarely used bits.
- Apply consistent ordering of imports and use of `module.exports` in testers.
- Remove some renaming of imports.
- Remove obsolete tests here and there.

services/npm/npm-base.js

@@ -2,8 +2,7 @@
 
 const Joi = require('joi')
 const serverSecrets = require('../../lib/server-secrets')
-const BaseJsonService = require('../base-json')
-const { InvalidResponse, NotFound } = require('../errors')
+const { BaseJsonService, InvalidResponse, NotFound } = require('..')
 const { isDependencyMap } = require('../package-json-helpers')
 
 const deprecatedLicenseObjectSchema = Joi.object({

services/npm/npm-collaborators.tester.js

@@ -2,7 +2,7 @@
 
 const Joi = require('joi')
 const { nonNegativeInteger } = require('../validators')
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('gets the contributor count')
   .get('/prettier.json')

services/npm/npm-dependency-version.tester.js

@@ -2,7 +2,7 @@
 
 const Joi = require('joi')
 const { semverRange } = require('../validators')
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('gets the peer dependency version')
   .get('/react-boxplot/peer/react.json')

services/npm/npm-downloads.service.js

@@ -1,8 +1,8 @@
 'use strict'
 
 const Joi = require('joi')
-const BaseJsonService = require('../base-json')
 const { metric } = require('../../lib/text-formatters')
+const { BaseJsonService } = require('..')
 const { nonNegativeInteger } = require('../validators')
 
 // https://github.com/npm/registry/blob/master/docs/download-counts.md#output

services/npm/npm-downloads.tester.js

@@ -1,7 +1,7 @@
 'use strict'
 
 const Joi = require('joi')
-const ServiceTester = require('../service-tester')
+const { ServiceTester } = require('..')
 const { isMetric } = require('../test-validators')
 
 const t = new ServiceTester({

services/npm/npm-license.tester.js

@@ -2,7 +2,7 @@
 
 const Joi = require('joi')
 
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('gets the license of express')
   .get('/express.json')

services/npm/npm-type-definitions.tester.js

@@ -6,7 +6,7 @@ const isTypeDefinition = Joi.string().regex(
   /^((Flow|TypeScript)|(Flow \| TypeScript))$/
 )
 
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('types (from dev dependencies + files)')
   .get('/chalk.json')

services/npm/npm-version.service.js

@@ -2,7 +2,7 @@
 
 const Joi = require('joi')
 const { renderVersionBadge } = require('../../lib/version')
-const { NotFound } = require('../errors')
+const { NotFound } = require('..')
 const NpmBase = require('./npm-base')
 
 const keywords = ['node']

services/npm/npm-version.tester.js

@@ -3,7 +3,7 @@
 const Joi = require('joi')
 const { isSemver } = require('../test-validators')
 
-const t = (module.exports = require('../create-service-tester')())
+const t = (module.exports = require('..').createServiceTester())
 
 t.create('gets the package version of left-pad')
   .get('/left-pad.json')