component-lifecycle-module.md

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title: Component lifecycle reorganization
pull_requests: [19543]

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To improve documentation, discoverability and internal organization, we've gathered all of the component lifecycle-related code we could and moved it into a dedicated lifecycle module.

The lifecycle / observer types (Add, Insert, Remove, Replace, Despawn) have been moved from the bevy_ecs::world to bevy_ecs::lifecycle.

The same move has been done for the more internal (but public) ComponentId constants: ADD, INSERT, REMOVE, REPLACE, DESPAWN.

The code for hooks (HookContext, ComponentHook, ComponentHooks) has been extracted from the very long bevy_ecs::components module, and now lives in the bevy_ecs::lifecycle module.

The RemovedComponents SystemParam, along with the public RemovedIter, RemovedIterWithId and RemovedComponentEvents have also been moved into this module as they serve a similar role. All references to bevy_ecs::removal_detection can be replaced with bevy_ecs::lifecycle.