basic resource client blurb

Author: patroza

wiki/ResourceClients.md

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+# Resource Clients
+
+We use Resource Clients to access Resources on the api.
+Internally it uses Effect RPC.
+
+## Query
+
+Queries are for reading data from the api. No writing/mutating allowed. Queries by default are deduplicated, shared between components, auto refreshed after stale time and user interaction with the tab/window.
+
+## Mutation
+
+Mutations are for writing data to the api, return values should at most include identifiers, and often `void`.
+Mutations auto invalidate Queries in their namespace, so that a Users.Index Query will be invalidated upon a Users.Delete or Update mutation.
+This only occurs within the same namespace, like "Users".
+If you need to invalidate queries in another namespace, you can pass the following option to the Mutation constructor: 
+
+```ts
+  queryInvalidation: (queryKey) => [
+    { filters: { queryKey } },
+    { filters: { queryKey: makeQueryKey(meClient.GetMe) } }
+  ]
+```
+
+## Command
+
+A Command captures the start of a user interaction (e.g button click), procceses the input, performs side effects,
+all of this wrapped in a tracing span and defect reporting. To handle status updated to the UI, Commands return Results, and you can compose various handling like automatic Toast on Wait, Succeed and Failure.
+All queries and mutations have a strict namespace and name, which is then used for span names, i18n, etc.