[DOCS][Developer] Elaborate on implementing and configuring a module

docs/developer/src/modules/configuration.md

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+# Adding configuration to a Module
+
+## The trade-off between re-usability and usability
+
+> The more general the interface, the greater the re-usability, but it is then more
+> complex and hence less usable.
+
+It is often good to find a compromise by means of configuration.
+
+## Module configuration
+
+The default configuration is placed in `local/plugins/Name/config.yaml`.
+
+```yaml
+parameters:
+  name:
+    setting: 42
+```
+
+A user can override this configuration in `social.local.yaml` with:
+
+```yaml
+parameters:
+  locals:
+    name:
+      setting: 1337
+```
+
+Note that if plugin's name is something like `FirstSecond`, it will become `first_second`
+in the configuration file.

docs/developer/src/modules/lifetime.md

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+Initialization
+--------------
+
+Plugins overload this method to do any initialization they need, like connecting
+to remote servers or creating paths or so on. @return bool hook value; true
+means continue processing, false means stop.
+
+```php
+public function initialize(): bool
+{
+    return true;
+}
+```
+
+Clean Up
+--------
+
+Plugins overload this method to do any cleanup they need, like disconnecting from
+remote servers or deleting temp files or so on.
+
+```php
+public function cleanup(): bool
+{
+    return true;
+}
+```

docs/developer/src/modules/sample_plugins/Awesomeness.md

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+# Awesomeness