Fix(crud) include param lookup now works w/plurals

Previously, {one,many}-to-many relationships with models would result in
`associationNames` that were plural. e.g. `Team` might have many
players and one location. The validation was expecting to see the plural
`Players` and the singular `Location` but Sequelize is expecting the
singular `Player` (`Location` worked fine). This meant that include
lookups would silently fail. This fixes the problem in a backward-
compatible way.

It continues to allow `include=Location` (capitalized) for backward-
compatibility. And now allows and actually does the lookup for
`include=players`, `include=player`, `include=Player`, `include=Players`
lookup relationships.

src/crud.js

@@ -55,7 +55,15 @@ models: {
 export default (server, model, { prefix, defaultConfig: config, models: permissions }) => {
   const modelName = model._singular;
   const modelAttributes = Object.keys(model.attributes);
-  const modelAssociations = Object.keys(model.associations);
+  const associatedModelNames = Object.keys(model.associations);
+  const modelAssociations = [
+    ...associatedModelNames,
+    ..._.flatMap(associatedModelNames, (associationName) => {
+      const { target } = model.associations[associationName];
+      const { _singular, _plural, _Singular, _Plural } = target;
+      return [_singular, _plural, _Singular, _Plural];
+    }),
+  ];
 
   const attributeValidation = modelAttributes.reduce((params, attribute) => {
     params[attribute] = joi.any();

src/index.js

@@ -32,6 +32,8 @@ const register = (server, options = {}, next) => {
     const { plural, singular } = model.options.name;
     model._plural = plural.toLowerCase();
     model._singular = singular.toLowerCase();
+    model._Plural = plural;
+    model._Singular = singular;
 
     // Join tables
     if (model.options.name.singular !== model.name) continue;

src/utils.js

@@ -20,6 +20,13 @@ export const parseInclude = request => {
   const { models } = noGetDb ? request : request.getDb();
 
   return include.map(a => {
+    const singluarOrPluralMatch = Object.keys(models).find((modelName) => {
+      const { _singular, _plural } = models[modelName];
+      return _singular === a || _plural === a;
+    });
+
+    if (singluarOrPluralMatch) return models[singluarOrPluralMatch];
+
     if (typeof a === 'string') return models[a];
 
     if (a && typeof a.model === 'string' && a.model.length) {