rpc: add chunked genesis endpoint (#299)

* rpc: add chunked genesis endpoint

* fix lint

* feedback

* add info about error

* fix lint

Co-authored-by: marbar3778 <marbar3778@yahoo.com>

spec/rpc/README.md

@@ -30,6 +30,7 @@ This file defines the JSON-RPC spec of Tendermint. This is meant to be implement
   | [Commit](#commit)                       |                             ✅                              |                                 ✅                                 |
   | [Validators](#validators)               |                             ✅                              |                                 ✅                                 |
   | [Genesis](#genesis)                     |                             ✅                              |                                 ✅                                 |
+  | [GenesisChunked](#genesischunked)       |                             ✅                              |                                 ❌                                 |
   | [ConsensusParams](#consensusparams)     |                             ✅                              |                                 ❌                                 |
   | [UnconfirmedTxs](#unconfirmedtxs)       |                             ✅                              |                                 ❌                                 |
   | [NumUnconfirmedTxs](#numunconfirmedtxs) |                             ✅                              |                                 ❌                                 |
@@ -796,7 +797,8 @@ curl -X POST https://localhost:26657 -d "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\
 
 ### Genesis
 
-Get Genesis of the chain.
+Get Genesis of the chain. If the response is large, this operation
+will return an error: use `genesis_chunked` instead.
 
 #### Request
 
@@ -856,6 +858,43 @@ curl -X POST https://localhost:26657 -d "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\
 }
 ```
 
+### GenesisChunked
+
+Get the genesis document in a chunks to support easily transfering larger documents.
+
+#### Parameters
+
+- `chunk` (integer): the index number of the chunk that you wish to
+  fetch. These IDs are 0 indexed.
+
+#### Request
+
+##### HTTP
+
+```sh
+curl  http://127.0.0.1:26657/genesis_chunked?chunk=0
+```
+
+##### JSONRPC
+
+```sh
+curl -X POST https://localhost:26657 -d "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"genesis_chunked\",\"params\":{\"chunk\":0}}"
+```
+
+#### Response
+
+```json
+{
+  "jsonrpc": "2.0",
+  "id": 0,
+  "result": {
+     "chunk": 0,
+     "total": 10,
+     "data": "dGVuZGVybWludAo="
+  }
+}
+```
+
 ### ConsensusParams
 
 Get the consensus parameters.