Updated test case documentation

docs/test_cases/t20015.md

@@ -0,0 +1,67 @@
+# t20015 - Class exclusion by namespace in sequence diagram test case
+## Config
+```yaml
+compilation_database_dir: ..
+output_directory: puml
+diagrams:
+  t20015_sequence:
+    type: sequence
+    glob:
+      - ../../tests/t20015/t20015.cc
+    include:
+      namespaces:
+        - clanguml::t20015
+    exclude:
+      namespaces:
+        - clanguml::t20015::detail
+    using_namespace:
+      - clanguml::t20015
+    start_from:
+      - function: "clanguml::t20015::tmain()"
+```
+## Source code
+File t20015.cc
+```cpp
+#include <memory>
+#include <optional>
+
+namespace clanguml {
+namespace t20015 {
+
+namespace detail {
+class A {
+public:
+    void set_x(int x) { x_ = x; }
+    void set_y(int y) { y_ = y; }
+    void set_z(int z) { z_ = z; }
+
+private:
+    int x_;
+    int y_;
+    int z_;
+};
+}
+
+class B {
+public:
+    void setup_a(std::shared_ptr<detail::A> &a)
+    {
+        a->set_x(1);
+        a.get()->set_y(2);
+        (*a).set_z(3);
+    }
+};
+
+void tmain()
+{
+    auto a = std::make_shared<detail::A>();
+
+    B b;
+
+    b.setup_a(a);
+}
+}
+}
+```
+## Generated UML diagrams
+![t20015_sequence](./t20015_sequence.svg "Class exclusion by namespace in sequence diagram test case")