add new functionality and improve backend server structure

- Enhance server functionality and optimize backend code
- Add multi-database support (PostgreSQL, MySQL, SQLite)

server/core_backend-server/tools/security/jwt.go

@@ -0,0 +1,56 @@
+package security
+
+import (
+	"errors"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+)
+
+// ParseUnverifiedJWT parses JWT and returns its claims
+// but DOES NOT verify the signature.
+//
+// It verifies only the exp, iat and nbf claims.
+func ParseUnverifiedJWT(token string) (jwt.MapClaims, error) {
+	claims := jwt.MapClaims{}
+
+	parser := &jwt.Parser{}
+	_, _, err := parser.ParseUnverified(token, claims)
+
+	if err == nil {
+		err = jwt.NewValidator(jwt.WithIssuedAt()).Validate(claims)
+	}
+
+	return claims, err
+}
+
+// ParseJWT verifies and parses JWT and returns its claims.
+func ParseJWT(token string, verificationKey string) (jwt.MapClaims, error) {
+	parser := jwt.NewParser(jwt.WithValidMethods([]string{"HS256"}))
+
+	parsedToken, err := parser.Parse(token, func(t *jwt.Token) (any, error) {
+		return []byte(verificationKey), nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	if claims, ok := parsedToken.Claims.(jwt.MapClaims); ok && parsedToken.Valid {
+		return claims, nil
+	}
+
+	return nil, errors.New("unable to parse token")
+}
+
+// NewJWT generates and returns new HS256 signed JWT.
+func NewJWT(payload jwt.MapClaims, signingKey string, duration time.Duration) (string, error) {
+	claims := jwt.MapClaims{
+		"exp": time.Now().Add(duration).Unix(),
+	}
+
+	for k, v := range payload {
+		claims[k] = v
+	}
+
+	return jwt.NewWithClaims(jwt.SigningMethodHS256, claims).SignedString([]byte(signingKey))
+}