Adding inital coding guidelines doc

coding_guidelines.md

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+<!-- ----------------------------------------------------------------------------
+  Copyright (c) 2026 Contributors to the Eclipse Foundation
+
+  See the NOTICE file(s) distributed with this work for additional
+  information regarding copyright ownership.
+
+  This program and the accompanying materials are made available under the
+  terms of the Apache License Version 2.0 which is available at
+  https://www.apache.org/licenses/LICENSE-2.0
+
+  SPDX-License-Identifier: Apache-2.0
+----------------------------------------------------------------------------- -->
+
+# Lifecycle Coding Guidelines
+
+## `Create` Method
+
+When a class can fail in the constructor create a static Create method that
+returns a `Result<T>`.
+
+## `auto` Usage
+
+Only use `auto` when it is obvious what the type will be.
+
+1. The full expression already specifies the type.
+   ```cpp
+   auto something = std::make_shared<int>(1);
+   ```
+1. The right hand side of the assignment is a standard (ISO C++, POSIX, SCORE)
+   function.
+   ```cpp
+    // Fine, this is a std function so it's understood what the types are.
+    std::unordered_map<int, std::string> data {};
+    auto res = data.insert(...);
+
+    // Fine, same as above
+    std::vector<int> other_data {}
+    for(auto& val: other_data)
+    {...}
+   ```
+1. Creating a lambda function.
+1. The type wraps another type, and is only used to check validity before
+   unwrapping to an object of another type.
+   ```cpp
+    auto something_res = SomeType::Create();
+    if (!something_res)
+    {...}
+    SomeType something = something_res.value();
+   ```
+
+Not allowed:
+```cpp
+// Not allowed, you'd have to look at the definition of the method to see what
+// the type is.
+auto something = someMethod();
+```
+
+## No Yoda Conditions
+
+https://en.wikipedia.org/wiki/Yoda_conditions#Criticism
+
+```cpp
+if (42 == value){}  // Bad
+
+if (value == 42){} // Good
+```
+
+## Namespaces
+
+For the namespace you shall use the following
+
+```
+score/
+├── health_monitor       // namespace score::mw::health
+│   └── src
+│       └── cpp          // Public API score::mw::health
+│           └── details  // Private API score::mw::health::internal::<component name>
+└── launch_manager       // namespace score::mw::lifecycle
+    └── src
+        └── alive        // Public API namespace score::mw::lifecycle
+            └── details  // Private API namespace score::mw::lifecycle::internal::<component name>
+```
+
+## Class Mocking
+
+The projects chosen method of mocking is dependency injection.
+And so all classes shall be designed such that they allow injecting mocks
+classes.
+
+## Bazel Visibility & Folder Structure
+
+The following rules shall be followed:
+
+1. Component directory (e.g. `osal`) can be visible to any target **inside**
+   the module.
+1. The visiblity in the Component directory shall be as strict as
+   possible.
+1. The `details` directory shall only be visible to the parent component.
+
+```
+score/launch_manager/src/daemon/src/
+└── osal   <- visibility = ["//score:__subpackages__"],
+    └── details   <- visibility = ["//score/launch_manager/src/daemon/src/osal:__subpackages__"],
+```
+
+## File Naming Conventions
+
+* All mocks shall be called `mock_<unit>.hpp`.
+* Headers with an interface shall have the `i` prefix. e.g. `icomponent.hpp`