docs: feegrant client spec (#10160)

* docs: feegrant client spec

* fix cli statement

Co-authored-by: Aleksandr Bezobchuk <alexanderbez@users.noreply.github.com>

x/feegrant/spec/05_client.md

@@ -0,0 +1,184 @@
+<!--
+order: 6
+-->
+
+# Client
+
+## CLI
+
+A user can query and interact with the `feegrant` module using the CLI.
+
+### Query
+
+The `query` commands allow users to query `feegrant` state.
+
+```
+simd query feegrant --help
+```
+
+#### grant
+
+The `grant` command allows users to query a grant for a given granter-grantee pair.
+
+```
+simd query feegrant grant [granter] [grantee] [flags]
+```
+
+Example:
+
+```
+simd query feegrant grant cosmos1.. cosmos1..
+```
+
+Example Output:
+
+```
+allowance:
+  '@type': /cosmos.feegrant.v1beta1.BasicAllowance
+  expiration: null
+  spend_limit:
+  - amount: "100"
+    denom: stake
+grantee: cosmos1..
+granter: cosmos1..
+```
+
+#### grants
+
+The `grants` command allows users to query all grants for a given grantee.
+
+```
+simd query feegrant grants [grantee] [flags]
+```
+
+Example:
+
+```
+simd query feegrant grants cosmos1..
+```
+
+Example Output:
+
+```
+allowances:
+- allowance:
+    '@type': /cosmos.feegrant.v1beta1.BasicAllowance
+    expiration: null
+    spend_limit:
+    - amount: "100"
+      denom: stake
+  grantee: cosmos1..
+  granter: cosmos1..
+pagination:
+  next_key: null
+  total: "0"
+```
+
+### Transactions
+
+The `tx` commands allow users to interact with the `feegrant` module.
+
+```
+simd tx feegrant --help
+```
+
+#### grant
+
+The `grant` command allows users to grant fee allowances to another account. The fee allowance can have an expiration date, a total spend limit, and/or a periodic spend limit.
+
+```
+simd tx feegrant grant [granter] [grantee] [flags]
+```
+
+Example (one-time spend limit):
+
+```
+simd tx feegrant grant cosmos1.. cosmos1.. --spend-limit 100stake
+```
+
+Example (periodic spend limit):
+
+```
+simd tx feegrant grant cosmos1.. cosmos1.. --period 3600 --period-limit 10stake
+```
+
+#### revoke
+
+The `revoke` command allows users to revoke a granted fee allowance.
+
+```
+simd tx feegrant revoke [granter] [grantee] [flags]
+```
+
+Example:
+
+```
+simd tx feegrant revoke cosmos1.. cosmos1..
+```
+
+## gRPC
+
+A user can query the `feegrant` module using gRPC endpoints.
+
+### Allowance
+
+The `Allowance` endpoint allows users to query a granted fee allowance.
+
+```
+cosmos.feegrant.v1beta1.Query/Allowance
+```
+
+Example:
+
+```
+grpcurl -plaintext \
+    -d '{"grantee":"cosmos1..","granter":"cosmos1.."}' \
+    localhost:9090 \
+    cosmos.feegrant.v1beta1.Query/Allowance
+```
+
+Example Output:
+
+```
+{
+  "allowance": {
+    "granter": "cosmos1..",
+    "grantee": "cosmos1..",
+    "allowance": {"@type":"/cosmos.feegrant.v1beta1.BasicAllowance","spendLimit":[{"denom":"stake","amount":"100"}]}
+  }
+}
+```
+
+### Allowances
+
+The `Allowances` endpoint allows users to query all granted fee allowances for a given grantee.
+
+```
+cosmos.feegrant.v1beta1.Query/Allowances
+```
+
+Example:
+
+```
+grpcurl -plaintext \
+    -d '{"address":"cosmos1.."}' \
+    localhost:9090 \
+    cosmos.feegrant.v1beta1.Query/Allowances
+```
+
+Example Output:
+
+```
+{
+  "allowances": [
+    {
+      "granter": "cosmos1..",
+      "grantee": "cosmos1..",
+      "allowance": {"@type":"/cosmos.feegrant.v1beta1.BasicAllowance","spendLimit":[{"denom":"stake","amount":"100"}]}
+    }
+  ],
+  "pagination": {
+    "total": "1"
+  }
+}
+```

x/feegrant/spec/README.md

@@ -30,3 +30,6 @@ This module allows accounts to grant fee allowances and to use fees from their a
     - [MsgGrantAllowance](04_events.md#msggrantallowance)
     - [MsgRevokeAllowance](04_events.md#msgrevokeallowance)
     - [Exec fee allowance](04_events.md#exec-fee-allowance)
+5. **[Client](05_client.md)**
+    - [CLI](05_client.md#cli)
+    - [gRPC](05_client.md#grpc)