feat(docs): added a rewards-api howto (#457)

* feat(docs): added a rewards-api howto

 - Rewards Api should be no longer experimental next release
 - There's some caveats to using it such as needing states, which may be confusing without guidance.
 - Added basic examples for each api request that wouldn't generate too much output.

 I think this has the basic concepts, but I couldn't easily link to the rewards endpoints doc,
 and I wasn't sure if i should link to the beacon-apis doc.

* docs: edits to content

* docs: address reviewer feedback

* docs: minor updates

* docs: add suggested content

* Update docs/how-to/use-rewards-api.md

---------

Co-authored-by: bgravenorst <byron.gravenorst@consensys.net>
Co-authored-by: Alexandra Tran Carrillo <12214231+alexandratran@users.noreply.github.com>

docs/how-to/use-rewards-api.md

@@ -0,0 +1,142 @@
+---
+description: Use the rewards API to view validator rewards.
+sidebar_position: 13
+---
+
+# View block rewards
+
+Use the [rewards API](https://consensys.github.io/teku/#tag/Rewards) to view the validator rewards.
+
+:::note
+
+You cannot query attestation rewards for the latest epoch.
+
+:::
+
+Enable the rewards API with the [`--rest-api-enabled`](../reference/cli/index.md#rest-api-enabled) command line option.
+
+:::tip
+
+A [Swagger interface is also available](../reference/rest.md#enable-the-rest-api-service). Use the [`--rest-api-docs-enabled`](../reference/cli/index.md#rest-api-docs-enabled) command line option to enable the web interface.
+
+:::
+
+## Limitations
+
+The following limitations apply:
+
+- The rewards API currently supports the `altair` fork upgrade and later.
+
+- The rewards API relies on state and block data to retrieve the reward information, meaning you'll receive limited data if the beacon node being queried is not an archive node.
+
+- You can only query blocks from finalized to head if you are in `prune` storage mode.
+
+## Impact of data storage modes
+
+:::tip
+
+You can change the [`data-storage-mode`](../reference/cli/index.md#data-storage-mode) without re-initializing your database.
+
+You can change the frequency that states are stored by specifying [`data-storage-archive-frequency`](../reference/cli#data-storage-archive-frequency), but it will only affect the state storage from the time that the change has been made. It will also directly impact the amount of disk space required by Teku.
+
+:::
+
+Consider using a beacon node with `archive` mode storage if you frequently call the rewards API on finalized data. However, this may produce slow results due to having to replay blocks due to the infrequent storage of states on disk (every 2048 slots by default).
+
+You can consider tuning your data storage to access data quicker, by storing more states (at the cost of disk space), for example, [setting the archive frequency](../reference/cli/index.md#data-storage-archive-frequency) to `256` or even `64`, and replaying less blocks.
+
+## Examples
+
+Query all the rewards from the block currently at head.
+
+<!--tabs-->
+
+# Example
+
+```bash
+curl http://localhost:5051/eth/v1/beacon/rewards/blocks/head |jq
+```
+
+# Result
+
+```json
+{
+  "execution_optimistic": false,
+  "finalized": false,
+  "data": {
+    "proposer_index": "555552",
+    "total": "1217168",
+    "attestations": "0",
+    "sync_aggregate": "1217168",
+    "proposer_slashings": "0",
+    "attester_slashings": "0"
+  }
+}
+```
+
+<!--/tabs-->
+
+Query all the sync committee rewards from the block at head for validator index 1.
+
+<!--tabs-->
+
+# Example
+
+```bash
+curl -X POST \
+     -H 'accept: application/json' \
+     -H 'Content-Type: application/json' \
+     http://localhost:5051/eth/v1/beacon/rewards/sync_committee/head \
+     -d '["1"]' |jq
+```
+
+# Result
+
+```json
+{
+  "execution_optimistic": false,
+  "finalized": false,
+  "data": [
+    {
+      "validator_index": "1",
+      "reward": "16778"
+    }
+  ]
+}
+```
+
+<!--/tabs-->
+
+Query attestation rewards from epoch 204644, just for validator index 0.
+
+<!--tabs-->
+
+# Example
+
+```bash
+curl -X POST \
+     -H 'accept: application/json' \
+     -H 'Content-Type: application/json' \
+     http://localhost:5051/eth/v1/beacon/rewards/attestations/204648 \
+     -d '["0"]' |jq
+```
+
+# Result
+
+```json
+ {
+  "execution_optimistic": false,
+  "finalized": true,
+  "data": {
+    "ideal_rewards": [...],
+    "total_rewards": [
+      {
+        "validator_index": "0",
+        "head": "3125",
+        "target": "6005",
+        "source": "3236"
+      }
+    ]
+  }
+}
+```