Update REST API docs to include default and max values for page_size

Related to #3135

Update REST APIs documentation to include default and max values for `page_size` flag

* **Client Code Changes**
  - Update `getStoreMessagesV3` function in `waku/waku_api/rest/store/client.nim` to set the default value of `page_size` to 20.

* **Handler Code Changes**
  - Update `installStoreApiHandlers` procedure in `waku/waku_api/rest/store/handlers.nim` to enforce the default value of `page_size` to 20.
  - Enforce the max value of `page_size` to 100 in `installStoreApiHandlers` procedure.

* **Documentation Changes**
  - Add a note in `docs/api/rest-api.md` mentioning the default value of `page_size` is 20 and the max value is 100.
  - Add a note in `docs/operators/how-to/configure-rest-api.md` mentioning the default value of `page_size` is 20 and the max value is 100.

docs/api/rest-api.md

@@ -38,6 +38,9 @@ A particular OpenAPI spec can be easily imported into [Postman](https://www.post
 curl http://localhost:8645/debug/v1/info -s | jq
 ```
 
+### Store API
+
+The `page_size` flag in the Store API has a default value of 20 and a max value of 100.
 
 ### Node configuration
 Find details [here](https://github.com/waku-org/nwaku/tree/master/docs/operators/how-to/configure-rest-api.md)

docs/operators/how-to/configure-rest-api.md

@@ -1,4 +1,3 @@
-
 # Configure a REST API node
 
 A subset of the node configuration can be used to modify the behaviour of the HTTP REST API.
@@ -21,3 +20,5 @@ Example:
 ```shell
 wakunode2 --rest=true
 ```
+
+The `page_size` flag in the Store API has a default value of 20 and a max value of 100.

waku/waku_api/rest/store/client.nim

@@ -57,7 +57,7 @@ proc getStoreMessagesV3*(
   # Optional cursor fields
   cursor: string = "", # base64-encoded hash
   ascending: string = "",
-  pageSize: string = "",
+  pageSize: string = "20", # default value is 20
 ): RestResponse[StoreQueryResponse] {.
   rest, endpoint: "/store/v3/messages", meth: HttpMethod.MethodGet
 .}

waku/waku_api/rest/store/handlers.nim

@@ -132,6 +132,14 @@ proc createStoreQuery(
     except CatchableError:
       return err("page size parsing error: " & getCurrentExceptionMsg())
 
+  # Enforce default value of page_size to 20
+  if parsedPagedSize.isNone():
+    parsedPagedSize = some(20)
+
+  # Enforce max value of page_size to 100
+  if parsedPagedSize.get() > 100:
+    parsedPagedSize = some(100)
+
   return ok(
     StoreQueryRequest(
       includeData: parsedIncludeData,