expose DBus interface method names as symbols

Enable a way to access the method names of a given DBus interface as a
constexpr symbol via the header.

4 use-cases:

- printing error / debug logs with the method name.
  e.g. 'error calling ${METHOD_NAME}'

- accessing DBus methods in applications which do not yet use the PDI
  generated bindings.

- preventing typos in DBus method names

- estimating the impact of removing a given DBus method from an
  interface. When using these symbols, it would cause a build failure in
  applications relying on the existence of that method.

This change is similar to [1] and goes into the same direction.

Tested: Newly written unit test passes.

References:
[1] d2571922bfdb4f6b41ba4fbc45b8a4272793fd40

Change-Id: Id423c3a668dd1a8346040f4380476d5e02468ddb
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/test/gen/server/TestWithMethod/meson.build b/test/gen/server/TestWithMethod/meson.build
new file mode 100644
index 0000000..43b045c
--- /dev/null
+++ b/test/gen/server/TestWithMethod/meson.build
@@ -0,0 +1,38 @@
+# Generated file; do not modify.
+
+sdbusplus_current_path = 'server/TestWithMethod'
+
+generated_sources += custom_target(
+    'server/TestWithMethod__cpp'.underscorify(),
+    input: ['../../../yaml/server/TestWithMethod.interface.yaml'],
+    output: [
+        'common.hpp',
+        'server.hpp',
+        'server.cpp',
+        'aserver.hpp',
+        'client.hpp',
+    ],
+    depend_files: sdbusplusplus_depfiles,
+    command: [
+        sdbuspp_gen_meson_prog,
+        '--command',
+        'cpp',
+        '--output',
+        meson.current_build_dir(),
+        '--tool',
+        sdbusplusplus_prog,
+        '--directory',
+        meson.current_source_dir() / '../../../yaml',
+        'server/TestWithMethod',
+    ],
+    install: should_generate_cpp,
+    install_dir: [
+        get_option('includedir') / sdbusplus_current_path,
+        get_option('includedir') / sdbusplus_current_path,
+        false,
+        get_option('includedir') / sdbusplus_current_path,
+        get_option('includedir') / sdbusplus_current_path,
+    ],
+    build_by_default: should_generate_cpp,
+)
+