Fix: Cast id to int on plurals

Threat the request param as integer
closes typicode#925, closes typicode#396

__tests__/server/plural-with-custom-foreign-key.js

@@ -100,7 +100,7 @@ describe('Server with custom foreign key', () => {
         .post('/posts/1/comments')
         .send({ body: 'foo' })
         .expect('Content-Type', /json/)
-        .expect({ id: 4, post_id: '1', body: 'foo' })
+        .expect({ id: 4, post_id: 1, body: 'foo' })
         .expect(201))
   })
 

__tests__/server/plural.js

@@ -554,7 +554,7 @@ describe('Server', () => {
         .post('/posts/1/comments')
         .send({ body: 'foo' })
         .expect('Content-Type', /json/)
-        .expect({ id: 6, postId: '1', body: 'foo' })
+        .expect({ id: 6, postId: 1, body: 'foo' })
         .expect(201))
   })
 

src/server/router/nested.js

@@ -17,7 +17,7 @@ module.exports = opts => {
   // Rewrite URL (/:resource/:id/:nested -> /:nested) and request body
   function post(req, res, next) {
     const prop = pluralize.singular(req.params.resource)
-    req.body[`${prop}${opts.foreignKeySuffix}`] = req.params.id
+    req.body[`${prop}${opts.foreignKeySuffix}`] = parseInt(req.params.id)
     req.url = `/${req.params.nested}`
     next()
   }

src/server/router/plural.js

@@ -281,7 +281,7 @@ module.exports = (db, name, opts) => {
   // PUT /name/:id
   // PATCH /name/:id
   function update(req, res, next) {
-    const id = req.params.id
+    const id = parseInt(req.params.id)
     let resource
 
     if (opts._isFake) {