structure app by rest api standards

add getusers
tidy up BusinessException

Azaion.Common/Extensions/QueryableExtensions.cs

@@ -0,0 +1,27 @@
+using System.Linq.Expressions;
+
+namespace Azaion.Common.Extensions;
+
+public static class QueryableExtensions
+{
+    /// <summary>
+    /// Adds Where true predicate only if result of condition is true.
+    /// If false predicate provided, uses it in case of false result
+    /// Useful for filters, when filters should be applied only when it was set (not NULL)
+    /// </summary>
+    public static IQueryable<TSource> WhereIf<TSource>(this IQueryable<TSource> query, bool? condition,
+        Expression<Func<TSource, bool>> truePredicate,
+        Expression<Func<TSource, bool>>? falsePredicate = null)
+    {
+        if (!condition.HasValue)
+            return query;
+
+        if (condition.Value)
+            return query.Where(truePredicate);
+
+        return falsePredicate != null
+            ? query.Where(falsePredicate)
+            : query;
+    }
+
+}