api: add pagination for guilds

start adding apiMessages

add apiMessages lib with tests

use apiMessage and fix tests

fix content tests

guilds pagination: add api docs

guilds pagination: improve api docs

test/api/v3/unit/libs/apiMessages.js

@@ -0,0 +1,31 @@
+import apiMessages from '../../../../../website/server/libs/apiMessages';
+
+describe('API Messages', () => {
+  const message = 'Only public guilds support pagination.';
+  it('returns an API message', () => {
+    expect(apiMessages('guildsOnlyPaginate')).to.equal(message);
+  });
+
+  it('throws if the API message does not exist', () => {
+    expect(() => apiMessages('iDoNotExist')).to.throw;
+  });
+
+  it('clones the passed variables', () => {
+    let vars = {a: 1};
+    sandbox.stub(_, 'clone').returns({});
+    apiMessages('guildsOnlyPaginate', vars);
+    expect(_.clone).to.have.been.called.once;
+    expect(_.clone).to.have.been.calledWith(vars);
+  });
+
+  it('pass the message through _.template', () => {
+    let vars = {a: 1};
+    let stub = sinon.stub().returns('string');
+    sandbox.stub(_, 'template').returns(stub);
+    apiMessages('guildsOnlyPaginate', vars);
+    expect(_.template).to.have.been.called.once;
+    expect(_.template).to.have.been.calledWith(message);
+    expect(stub).to.have.been.called.once;
+    expect(stub).to.have.been.calledWith(vars);
+  });
+});