Implement + test unique slugs for user

I put the relevant line on categories and organizations too, but I
didn't test it separately. I could have tested it but found it
unnecessary repeating

src/middleware/sluggifyMiddleware.js

@@ -17,35 +17,19 @@ export default {
   Mutation: {
     CreatePost: async (resolve, root, args, context, info) => {
       args.slug = args.slug || await uniqueSlug(args.title, isUniqueFor(context, 'Post'))
-      const result = await resolve(root, args, context, info)
-      return result
+      return resolve(root, args, context, info)
     },
     CreateUser: async (resolve, root, args, context, info) => {
-      if (!args.slug) {
-        args.slug = slug(args.name, {
-          lower: true
-        })
-      }
-      const result = await resolve(root, args, context, info)
-      return result
+      args.slug = args.slug || await uniqueSlug(args.name, isUniqueFor(context, 'User'))
+      return resolve(root, args, context, info)
     },
     CreateOrganization: async (resolve, root, args, context, info) => {
-      if (!args.slug) {
-        args.slug = slug(args.name, {
-          lower: true
-        })
-      }
-      const result = await resolve(root, args, context, info)
-      return result
+      args.slug = args.slug || await uniqueSlug(args.name, isUniqueFor(context, 'Organization'))
+      return  resolve(root, args, context, info)
     },
     CreateCategory: async (resolve, root, args, context, info) => {
-      if (!args.slug) {
-        args.slug = slug(args.name, {
-          lower: true
-        })
-      }
-      const result = await resolve(root, args, context, info)
-      return result
+      args.slug = args.slug || await uniqueSlug(args.name, isUniqueFor(context, 'Category'))
+      return  resolve(root, args, context, info)
     }
   }
 }

src/middleware/slugifyMiddleware.spec.js

@@ -16,7 +16,7 @@ afterEach(async () => {
 
 describe('slugify', () => {
   describe('CreatePost', () => {
-    it('generates a slug based on the title', async () => {
+    it('generates a slug based on title', async () => {
       const response = await client.request(`mutation {
         CreatePost(
           title: "I am a brand new post",
@@ -44,7 +44,7 @@ describe('slugify', () => {
         expect(response).toEqual({ CreatePost: { slug: 'pre-existing-post-1' } })
       })
 
-      describe('but if the client requested a slug', () => {
+      describe('but if the client specifies a slug', () => {
         it('rejects CreatePost', async () => {
           await expect(client.request(`mutation {
               CreatePost(
@@ -58,4 +58,38 @@ describe('slugify', () => {
       })
     })
   })
+
+  describe('CreateUser', () => {
+    const action = async (mutation, params) => {
+      return client.request(`mutation {
+        ${mutation}(password: "yo", ${params}) { slug }
+      }`, { headers })
+    }
+    it('generates a slug based on name', async () => {
+      await expect(action('CreateUser', 'name: "I am a user"'))
+        .resolves.toEqual({ CreateUser: { slug: 'i-am-a-user' } })
+    })
+
+    describe('if slug exists', () => {
+      beforeEach(async () => {
+        await action('CreateUser', 'name: "Pre-existing user", slug: "pre-existing-user"')
+      })
+
+      it('chooses another slug', async () => {
+        await expect(action(
+          'CreateUser',
+          'name: "pre-existing-user"'
+        )).resolves.toEqual({ CreateUser: { slug: 'pre-existing-user-1' } })
+      })
+
+      describe('but if the client specifies a slug', () => {
+        it('rejects CreateUser', async () => {
+          await expect(action(
+            'CreateUser',
+            'name: "Pre-existing user", slug: "pre-existing-user"'
+          )).rejects.toThrow('already exists')
+        })
+      })
+    })
+  })
 })