DOC-5353 RS: Added common extra_info_keys to the shards REST API reference

Author: rrelledge

content/operate/rs/references/rest-api/requests/shards/_index.md

@@ -40,7 +40,7 @@ Get information about all shards in the cluster.
 
 | Field | Type | Description |
 |-------|------|-------------|
-| extra_info_keys | list of strings | A list of extra keys to be fetched (optional) |
+| extra_info_keys | list of strings | An optional list of extra keys to be fetched from the Redis [`INFO`]({{< relref "/commands/info" >}}) command. See [extra_info_keys](#extra_info_keys) for common keys to include. |
 
 ### Response {#get-all-response} 
 
@@ -68,7 +68,7 @@ Returns a JSON array of [shard objects]({{<relref "/operate/rs/references/rest-a
     "status": "active"
   },
   {
-    "uid": 2,
+    "uid": "2",
     "role": "slave",
     // additional fields...
   }
@@ -110,7 +110,7 @@ Gets information about a single shard.
 
 | Field | Type | Description |
 |-------|------|-------------|
-| extra_info_keys | list of strings | A list of extra keys to be fetched (optional) |
+| extra_info_keys | list of strings | An optional list of extra keys to be fetched from the Redis [`INFO`]({{< relref "/commands/info" >}}) command. See [extra_info_keys](#extra_info_keys) for common keys to include. |
 
 ### Response {#get-response} 
 
@@ -144,3 +144,71 @@ Returns a [shard object]({{<relref "/operate/rs/references/rest-api/objects/shar
 |------|-------------|
 | [200 OK](https://www.rfc-editor.org/rfc/rfc9110.html#name-200-ok) | No error. |
 | [404 Not Found](https://www.rfc-editor.org/rfc/rfc9110.html#name-404-not-found) | Shard UID does not exist. |
+
+## extra_info_keys
+
+You can include any Redis [`INFO`]({{< relref "/commands/info" >}}) command key for shard requests using the `extra_info_keys` query parameter. The requested keys are returned in the `redis_info` object of the response.
+
+See the following tables for common keys to include.
+
+### Client keys
+
+| Key | Type | Description |
+|-----|------|-------------|
+| blocked_clients | integer | Number of clients pending on a blocking call |
+| client_recent_max_input_buffer | integer | Biggest input buffer among current client connections |
+| client_recent_max_output_buffer | integer | Biggest output buffer among current client connections |
+| connected_clients | integer | Number of client connections, excluding connections from replicas |
+
+### Memory keys
+
+| Key | Type | Description |
+|-----|------|-------------|
+| maxmemory | integer | Value of the maxmemory configuration directive |
+| used_memory | integer | Total number of bytes allocated by Redis |
+| used_memory_dataset | integer | Size in bytes of the dataset |
+| used_memory_lua | integer | Number of bytes used by the Lua engine |
+| used_memory_overhead | integer | Sum of all overheads that the server allocated for managing its internal data structures |
+| used_memory_peak | integer | Peak memory in bytes consumed by Redis |
+| used_memory_rss | integer | Number of bytes that Redis allocated as seen by the operating system |
+
+### Persistence keys
+
+| Key | Type | Description |
+|-----|------|-------------|
+| aof_enabled | integer | Flag indicating append-only file (AOF) logging is activated |
+| aof_rewrite_in_progress | integer | Flag indicating an AOF rewrite operation is on-going |
+| rdb_bgsave_in_progress | integer | Flag indicating an RDB save is on-going |
+| rdb_changes_since_last_save | integer | Number of changes since the last dump |
+| rdb_last_bgsave_status | string | Status of the last RDB save operation |
+| rdb_last_save_time | integer | Epoch-based timestamp of last successful RDB save |
+
+### Replication keys
+
+| Key | Type | Description |
+|-----|------|-------------|
+| master_last_io_seconds_ago | integer | Number of seconds since the last interaction with the primary shard |
+| master_repl_offset | integer | The server's current replication offset |
+| slave_repl_offset | integer | Replication offset of the replica instance |
+
+### Server keys
+
+| Key | Type | Description |
+|-----|------|-------------|
+| configured_hz | integer | Server's configured frequency setting |
+| hz | integer | Server's current frequency setting |
+| redis_version | string | Version of the Redis server |
+| uptime_in_days | integer | Number of days since Redis server start |
+| uptime_in_seconds | integer | Number of seconds since Redis server start |
+
+### Statistics keys
+
+| Key | Type | Description |
+|-----|------|-------------|
+| instantaneous_ops_per_sec | integer | Number of commands processed per second |
+| keyspace_hits | integer | Number of successful lookup of keys in the main dictionary |
+| keyspace_misses | integer | Number of failed lookup of keys in the main dictionary |
+| total_commands_processed | integer | Total number of commands processed by the server |
+| total_connections_received | integer | Total number of connections accepted by the server |
+| total_net_input_bytes | integer | Total number of bytes read from the network |
+| total_net_output_bytes | integer | Total number of bytes written to the network |