DEV: Stop injecting a service result object in the caller object

Currently, when calling a service with its block form, a `#result`
method is automatically created on the caller object. Even if it never
clashed so far, this could happen.

This patch removes that method, and instead use a more classical way of
doing things: the result object is now provided as an argument to the
main block. This means if we need to access the result object in an
outcome block, it will be done like this from now on:
```ruby
MyService.call(params) do |result|
  on_success do
    # do something with the result object
    do_something(result)
  end
end
```

In the same vein, this patch introduces the ability to match keys from
the result object in the outcome blocks, like we already do with step
definitions in a service. For example:
```ruby
on_success do |model:, contract:|
  do_something(model, contract)
end
```
Instead of
```ruby
on_success do
  do_something(result.model, result.contract)
end
```

spec/lib/service/runner_spec.rb

@@ -150,10 +150,13 @@ RSpec.describe Service::Runner do
   describe ".call" do
     subject(:runner) { described_class.call(service, &actions_block) }
 
-    let(:result) { object.result }
     let(:actions_block) { object.instance_eval(actions) }
-    let(:service) { SuccessService }
-    let(:actions) { "proc {}" }
+    let(:service) { SuccessWithModelService }
+    let(:actions) { <<-BLOCK }
+        proc do |result|
+          on_success { |fake_model:| [result, fake_model] }
+        end
+      BLOCK
     let(:object) do
       Class
         .new(ApplicationController) do
@@ -171,10 +174,12 @@ RSpec.describe Service::Runner do
         .new
     end
 
-    it "runs the provided service in the context of a controller" do
-      runner
-      expect(result).to be_a Service::Base::Context
-      expect(result).to be_a_success
+    it "allows access to the result object" do
+      expect(runner.first).to be_a Service::Base::Context
+    end
+
+    it "allows using keyword args in blocks" do
+      expect(runner.last).to eq :model_found
     end
 
     context "when using the on_success action" do
@@ -241,7 +246,7 @@ RSpec.describe Service::Runner do
 
         context "when using the block argument" do
           let(:actions) { <<-BLOCK }
-              proc do
+              proc do |result|
                 on_failed_policy(:test) { |policy| policy == result["result.policy.test"] }
               end
             BLOCK
@@ -279,7 +284,7 @@ RSpec.describe Service::Runner do
 
         context "when using the block argument" do
           let(:actions) { <<-BLOCK }
-              proc do
+              proc do |result|
                 on_failed_contract { |contract| contract == result["result.contract.default"] }
               end
             BLOCK
@@ -301,8 +306,9 @@ RSpec.describe Service::Runner do
 
     context "when using the on_model_not_found action" do
       let(:actions) { <<-BLOCK }
-          proc do
-            on_model_not_found(:fake_model) { :no_model }
+          proc do |result|
+            on_success { [result] }
+            on_model_not_found(:fake_model) { [:no_model, result] }
           end
         BLOCK
 
@@ -311,7 +317,7 @@ RSpec.describe Service::Runner do
           let(:service) { FailureWithOptionalModelService }
 
           it "does not run the provided block" do
-            expect(runner).not_to eq :no_model
+            expect(runner).not_to include :no_model
           end
         end
 
@@ -320,13 +326,13 @@ RSpec.describe Service::Runner do
 
           context "when not using the block argument" do
             it "runs the provided block" do
-              expect(runner).to eq :no_model
+              expect(runner).to include :no_model
             end
           end
 
           context "when using the block argument" do
             let(:actions) { <<-BLOCK }
-                proc do
+                proc do |result|
                   on_model_not_found(:fake_model) { |model| model == result["result.model.fake_model"] }
                 end
               BLOCK
@@ -341,7 +347,7 @@ RSpec.describe Service::Runner do
           let(:service) { SuccessWithModelService }
 
           it "does not run the provided block" do
-            expect(runner).not_to eq :no_model
+            expect(runner).not_to include :no_model
           end
         end
       end
@@ -351,7 +357,7 @@ RSpec.describe Service::Runner do
           let(:service) { FailureWithCollectionModelService }
 
           it "runs the provided block" do
-            expect(runner).to eq :no_model
+            expect(runner).to include :no_model
           end
         end
 
@@ -359,7 +365,7 @@ RSpec.describe Service::Runner do
           let(:service) { SuccessWithCollectionModelService }
 
           it "does not run the provided block" do
-            expect(runner).not_to eq :no_model
+            expect(runner).not_to include :no_model
           end
         end
       end
@@ -371,23 +377,21 @@ RSpec.describe Service::Runner do
           before { Fabricate(:user) }
 
           it "does not run the provided block" do
-            expect(runner).not_to eq :no_model
+            expect(runner).not_to include :no_model
           end
 
           it "does not fetch records from the relation" do
-            runner
-            expect(result[:fake_model]).not_to be_loaded
+            expect(runner.last[:fake_model]).not_to be_loaded
           end
         end
 
         context "when the service fails" do
           it "runs the provided block" do
-            expect(runner).to eq :no_model
+            expect(runner).to include :no_model
           end
 
           it "does not fetch records from the relation" do
-            runner
-            expect(result[:fake_model]).not_to be_loaded
+            expect(runner.last[:fake_model]).not_to be_loaded
           end
         end
       end