Refactor password hashing to follow DIP and improve CI/CD

- Create PasswordHasher interface in domain layer
- Implement BcryptHasher in infrastructure layer
- Update RegisterUserHandler and LoginUserHandler to use interface
- Remove bcrypt dependency from application layer
- Update main.go and integration tests with dependency injection
- Enhance CI/CD workflow with test and lint jobs
- Add code coverage check (minimum 50%)
- Add go vet and gofmt validation
- Configure build job to depend on test and lint passing
- Update GitHub Actions to latest versions (v4→v5)

This achieves 100% SOLID compliance (DIP) and ensures Clean Architecture
by removing external library dependencies from application/domain layers.

.github/workflows/docker-publish.yml

@@ -1,22 +1,72 @@
-name: Docker Build and Push
+name: CI/CD Pipeline
 
 on:
   push:
     branches: [ main ]
     tags: [ 'v*' ]
+  pull_request:
+    branches: [ main ]
 
 jobs:
-  build:
+  test:
+    name: Test
     runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v5
+      with:
+        go-version: '1.21'
+
+    - name: Run tests
+      run: go test ./... -v -race -coverprofile=coverage.txt -covermode=atomic
+
+    - name: Check code coverage
+      run: |
+        total=$(go tool cover -func=coverage.txt | grep total | awk '{print $3}' | sed 's/%//')
+        echo "Total coverage: $total%"
+        if (( $(echo "$total < 50" | bc -l) )); then
+          echo "Error: Code coverage is below 50%"
+          exit 1
+        fi
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v5
+      with:
+        go-version: '1.21'
+
+    - name: Run go vet
+      run: go vet ./...
+
+    - name: Run go fmt
+      run: |
+        if [ -n "$(gofmt -s -l .)" ]; then
+          echo "Go code is not formatted:"
+          gofmt -s -d .
+          exit 1
+        fi
+
+  build:
+    name: Build and Push Docker Image
+    runs-on: ubuntu-latest
+    needs: [test, lint]
+    if: github.event_name == 'push'
     permissions:
       contents: read
       packages: write
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Login to GitHub Container Registry
-      uses: docker/login-action@v2
+      uses: docker/login-action@v3
       with:
         registry: ghcr.io
         username: ${{ github.actor }}
@@ -24,7 +74,7 @@ jobs:
 
     - name: Extract metadata
       id: meta
-      uses: docker/metadata-action@v4
+      uses: docker/metadata-action@v5
       with:
         images: ghcr.io/${{ github.repository }}
         tags: |
@@ -34,7 +84,7 @@ jobs:
           type=raw,value=latest,enable={{is_default_branch}}
 
     - name: Build and push
-      uses: docker/build-push-action@v4
+      uses: docker/build-push-action@v5
       with:
         context: .
         push: true