feat: api key authentication (#291)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/middleware/api_key_auth.go

@@ -0,0 +1,50 @@
+package middleware
+
+import (
+	"github.com/gin-gonic/gin"
+	"github.com/pocket-id/pocket-id/backend/internal/common"
+	"github.com/pocket-id/pocket-id/backend/internal/service"
+)
+
+type ApiKeyAuthMiddleware struct {
+	apiKeyService *service.ApiKeyService
+	jwtService    *service.JwtService
+}
+
+func NewApiKeyAuthMiddleware(apiKeyService *service.ApiKeyService, jwtService *service.JwtService) *ApiKeyAuthMiddleware {
+	return &ApiKeyAuthMiddleware{
+		apiKeyService: apiKeyService,
+		jwtService:    jwtService,
+	}
+}
+
+func (m *ApiKeyAuthMiddleware) Add(adminRequired bool) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		userID, isAdmin, err := m.Verify(c, adminRequired)
+		if err != nil {
+			c.Abort()
+			c.Error(err)
+			return
+		}
+
+		c.Set("userID", userID)
+		c.Set("userIsAdmin", isAdmin)
+		c.Next()
+	}
+}
+
+func (m *ApiKeyAuthMiddleware) Verify(c *gin.Context, adminRequired bool) (userID string, isAdmin bool, err error) {
+	apiKey := c.GetHeader("X-API-KEY")
+
+	user, err := m.apiKeyService.ValidateApiKey(apiKey)
+	if err != nil {
+		return "", false, &common.NotSignedInError{}
+	}
+
+	// Check if the user is an admin
+	if adminRequired && !user.IsAdmin {
+		return "", false, &common.MissingPermissionError{}
+	}
+
+	return user.ID, user.IsAdmin, nil
+}