Added serialization to create JSON object for Evidence

Added serializers which will create the Summary JSON.
Added spec files for the serializer and entities.

app/serializers/evidence_author_entity.rb

+# frozen_string_literal: true
+
+class EvidenceAuthorEntity < Grape::Entity
+  expose :id
+  expose :name
+  expose :email
+end

app/serializers/evidence_issue_entity.rb

+# frozen_string_literal: true
+
+class EvidenceIssueEntity < Grape::Entity
+  expose :id
+  expose :title
+  expose :description
+  expose :author, using: EvidenceAuthorEntity
+  expose :state
+  expose :confidential
+  expose :created_at
+  expose :due_date
+end

app/serializers/evidence_milestone_entity.rb

+# frozen_string_literal: true
+
+class EvidenceMilestoneEntity < Grape::Entity
+  expose :id
+  expose :title
+  expose :description
+  expose :state
+  expose :created_at
+  expose :due_date
+  expose :issues, using: EvidenceIssueEntity
+end

app/serializers/evidence_project_entity.rb

+# frozen_string_literal: true
+
+class EvidenceProjectEntity < Grape::Entity
+  expose :id
+  expose :name
+  expose :description
+  expose :created_at
+end

app/serializers/evidence_release_entity.rb

+# frozen_string_literal: true
+
+class EvidenceReleaseEntity < Grape::Entity
+  expose :id
+  expose :tag
+  expose :name
+  expose :description
+  expose :created_at
+  expose :project, using: EvidenceProjectEntity
+  expose :milestones, using: EvidenceMilestoneEntity
+end

app/serializers/evidence_release_serializer.rb

+# frozen_string_literal: true
+
+class EvidenceReleaseSerializer < BaseSerializer
+  entity EvidenceReleaseEntity
+end

spec/serializers/evidence_author_entity_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe EvidenceAuthorEntity do
+  let(:entity) { described_class.new(build(:author)) }
+
+  subject { entity.as_json }
+
+  it 'exposes the expected fields' do
+    expect(subject.keys).to contain_exactly(:id, :name, :email)
+  end
+end

spec/serializers/evidence_issue_entity_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe EvidenceIssueEntity do
+  let(:entity) { described_class.new(build(:issue)) }
+
+  subject { entity.as_json }
+
+  it 'exposes the expected fields' do
+    expect(subject.keys).to contain_exactly(:id, :title, :description, :author, :state, :confidential, :created_at, :due_date)
+  end
+end

spec/serializers/evidence_milestone_entity_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe EvidenceMilestoneEntity do
+  let(:milestone) { build(:milestone) }
+  let(:entity) { described_class.new(milestone) }
+
+  subject { entity.as_json }
+
+  it 'exposes the expected fields' do
+    expect(subject.keys).to contain_exactly(:id, :title, :description, :state, :created_at, :due_date, :issues)
+  end
+
+  context 'when there issues linked to this milestone' do
+    let(:issue_1) { build(:issue) }
+    let(:issue_2) { build(:issue) }
+    let(:milestone) { build(:milestone, issues: [issue_1, issue_2]) }
+
+    it 'exposes these issues' do
+      expect(subject[:issues]).to contain_exactly(
+        EvidenceIssueEntity.new(issue_1).as_json,
+        EvidenceIssueEntity.new(issue_2).as_json
+      )
+    end
+  end
+
+  context 'when the release has no milestone' do
+    let(:milestone) { build(:milestone, issues: []) }
+
+    it 'exposes an empty array for milestones' do
+      expect(subject[:issues]).to be_empty
+    end
+  end
+end

spec/serializers/evidence_project_entity_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe EvidenceProjectEntity do
+  let(:entity) { described_class.new(build(:project)) }
+
+  subject { entity.as_json }
+
+  it 'exposes the expected fields' do
+    expect(subject.keys).to contain_exactly(:id, :name, :description, :created_at)
+  end
+end

spec/serializers/evidence_release_entity_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe EvidenceReleaseEntity do
+  let(:release) { build(:release) }
+  let(:entity) { described_class.new(release) }
+
+  subject { entity.as_json }
+
+  it 'exposes the expected fields' do
+    expect(subject.keys).to contain_exactly(:id, :tag, :name, :description, :created_at, :project, :milestones)
+  end
+
+  context 'when the release has milestones' do
+    let(:project) { create(:project) }
+    let(:milestone_1) { build(:milestone, project: project) }
+    let(:milestone_2) { build(:milestone, project: project) }
+    let(:release) { build(:release, project: project, milestones: [milestone_1, milestone_2]) }
+
+    it 'exposes these milestones' do
+      expect(subject[:milestones]).to contain_exactly(
+        EvidenceMilestoneEntity.new(milestone_1).as_json,
+        EvidenceMilestoneEntity.new(milestone_2).as_json
+      )
+    end
+  end
+
+  context 'when the release has no milestone' do
+    let(:release) { build(:release, milestones: []) }
+
+    it 'exposes an empty array for milestones' do
+      expect(subject[:milestones]).to be_empty
+    end
+  end
+end

spec/serializers/evidence_release_serializer_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe EvidenceReleaseSerializer do
+  it 'represents an EvidenceReleaseEntity entity' do
+    expect(described_class.entity_class).to eq(EvidenceReleaseEntity)
+  end
+end