basic-price-oracle: specify error code

Simply passes an error code of 1 (unsupported subject asset) where
appropriate in the mock oracle. The raw code is used instead of
oraclerpc.UNSUPPORTED or similar to avoid dependency changes at present.

Also adds the mock oracle's log to gitignore.

Author: jtobin

.gitignore

@@ -24,6 +24,7 @@ cmd/tapd/tapd
 /itest/itest.test
 
 /docs/examples/basic-price-oracle/basic-price-oracle
+/docs/examples/basic-price-oracle/basic-price-oracle-example.log
 
 # Load test binaries and config
 /loadtest

docs/examples/basic-price-oracle/main.go

@@ -306,6 +306,7 @@ func (p *RpcPriceOracleServer) QueryAssetRates(_ context.Context,
 				Error: &oraclerpc.QueryAssetRatesErrResponse{
 					Message: "unsupported payment asset, " +
 						"only BTC is supported",
+					Code: 1,
 				},
 			},
 		}, nil
@@ -326,6 +327,7 @@ func (p *RpcPriceOracleServer) QueryAssetRates(_ context.Context,
 			Result: &oraclerpc.QueryAssetRatesResponse_Error{
 				Error: &oraclerpc.QueryAssetRatesErrResponse{
 					Message: "unsupported subject asset",
+					Code: 1,
 				},
 			},
 		}, nil