Add new GraphQL types, schema (with fields) & base mutation

The current consul GraphQL API has two problems.

1) It uses some unnecessary complicated magic to automatically create
   the GraphQL types and querys using an `api.yml` file. This approach
   is over-engineered, complex and has no benefits. It's just harder to
   understand the code for people which are not familiar with the
   project (like me, lol).

2) It uses a deprecated DSL [1] that is soon going to be removed from
   `graphql-ruby` completely. We are already seeing deprecation warning
   because of this (see References).

There was one problem. I wanted to create the API so that it is fully
backwards compatible with the old one, BUT the old one uses field names
which are directly derived from the ruby code, which results in
snake_case field names - not the GraphQL way. When I'm using the
graphql-ruby Class-based syntax, it automatically creates the fields in
camelCase, which breaks backwards-compatibility.

So I've added deprecated snake_case field names to keep it
backwards-compatible.

[1] https://graphql-ruby.org/schema/class_based_api.html

spec/lib/graphql_spec.rb

@@ -1,12 +1,5 @@
 require "rails_helper"
 
-api_types  = GraphQL::ApiTypesCreator.create
-query_type = GraphQL::QueryTypeCreator.create(api_types)
-ConsulSchema = GraphQL::Schema.define do
-  query query_type
-  max_depth 12
-end
-
 def execute(query_string, context = {}, variables = {})
   ConsulSchema.execute(query_string, context: context, variables: variables)
 end
@@ -40,8 +33,8 @@ describe "Consul Schema" do
   let(:proposal) { create(:proposal, author: user) }
 
   it "returns fields of Int type" do
-    response = execute("{ proposal(id: #{proposal.id}) { id } }")
-    expect(dig(response, "data.proposal.id")).to eq(proposal.id)
+    response = execute("{ proposal(id: #{proposal.id}) { cached_votes_up } }")
+    expect(dig(response, "data.proposal.cached_votes_up")).to eq(proposal.cached_votes_up)
   end
 
   it "returns fields of String type" do
@@ -373,6 +366,17 @@ describe "Consul Schema" do
       expect(received_comments).not_to include(not_public_poll_comment.body)
     end
 
+    it "only links public comments" do
+      user = create(:administrator).user
+      create(:comment, author: user, body: "Public")
+      create(:budget_investment_comment, author: user, valuation: true, body: "Valuation")
+
+      response = execute("{ user(id: #{user.id}) { public_comments { edges { node { body } } } } }")
+      received_comments = dig(response, "data.user.public_comments.edges")
+
+      expect(received_comments).to eq [{ "node" => { "body" => "Public" }}]
+    end
+
     it "only returns date and hour for created_at" do
       created_at = Time.zone.parse("2017-12-31 9:30:15")
       create(:comment, created_at: created_at)