refactor routes,

use json encoding for route body parameters,
implement modify user/group/pool operations,
simplify schema by using comon lib struct tags and RequireAll and AtLeastOne helper functions,
properly implement locadb as Backend interface

app/common/utils.go

@@ -0,0 +1,55 @@
+package app
+
+import (
+	"reflect"
+)
+
+// RequireAll ensures that EVERY non-excluded exported field in the struct is non-zero.
+func RequireAll(v any, excludes ...string) bool {
+	val := reflect.ValueOf(v)
+	if val.Kind() == reflect.Pointer {
+		val = val.Elem()
+	}
+	typ := val.Type()
+
+	excludeMap := make(map[string]bool)
+	for _, ex := range excludes {
+		excludeMap[ex] = true
+	}
+
+	for i := 0; i < val.NumField(); i++ {
+		fieldName := typ.Field(i).Name
+		if excludeMap[fieldName] {
+			continue
+		}
+		if val.Field(i).IsZero() {
+			return false
+		}
+	}
+	return true
+}
+
+// AtLeastOne ensures that AT LEAST ONE non-excluded exported field is non-zero.
+func AtLeastOne(v any, excludes ...string) bool {
+	val := reflect.ValueOf(v)
+	if val.Kind() == reflect.Pointer {
+		val = val.Elem()
+	}
+	typ := val.Type()
+
+	excludeMap := make(map[string]bool)
+	for _, ex := range excludes {
+		excludeMap[ex] = true
+	}
+
+	for i := 0; i < val.NumField(); i++ {
+		fieldName := typ.Field(i).Name
+		if excludeMap[fieldName] {
+			continue
+		}
+		if !val.Field(i).IsZero() {
+			return true
+		}
+	}
+	return false
+}