Switch protobuf generation to buf cli tool (#720)

Current generation of protobuf stubs is hard and there's open issues
around it:
   https://github.com/grpc-ecosystem/grpc-gateway/issues/1065

grpc-gateway author and README suggest to use `buf` instead which
intends to be a simpler and more reliable method of protobuf stub
generation.

gctrpc/README.md

@@ -36,10 +36,11 @@ manager or by downloading one of the releases from the official repository:
 Then use `go get` to download the following packages:
 
 ```bash
-go get github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-grpc-gateway
-go get github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-openapiv2
-go get google.golang.org/protobuf/cmd/protoc-gen-go
-go get google.golang.org/grpc/cmd/protoc-gen-go-grpc
+go get \
+    github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-grpc-gateway \
+    github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-openapiv2 \
+    google.golang.org/protobuf/cmd/protoc-gen-go \
+    google.golang.org/grpc/cmd/protoc-gen-go-grpc
 ```
 
 This will place the following binaries in your `$GOBIN`;
@@ -51,15 +52,25 @@ This will place the following binaries in your `$GOBIN`;
 
 Make sure that your `$GOBIN` is in your `$PATH`.
 
-## Usage
+### Linux / macOS
+
+GoCryptoTrader requires a local installation of the `buf` cli tool that tries to make Protobuf handling more easier and reliable,
+after [installation](https://docs.buf.build/installation) you'll need to run:
+
+```shell
+buf beta mod update
+```
+
+After previous command, make necessary changes to the `rpc.proto` spec file and run the generation command:
+
+```shell
+buf generate
+```
+
+### Windows
 
 After the above dependencies are required, make necessary changes to the `rpc.proto`
 spec file and run the generation scripts:
 
-### Windows
-
 Run `gen_pb_win.bat`
 
-### Linux and macOS
-
-Run `./gen_pb_linux.sh`

gctrpc/buf.gen.yaml

@@ -0,0 +1,17 @@
+version: v1beta1
+plugins:
+  - name: go
+    out: ./
+    opt:
+      - paths=source_relative
+  - name: go-grpc 
+    out: ./
+    opt:
+      - paths=source_relative
+  - name: grpc-gateway
+    out: ./
+    opt:
+      - paths=source_relative
+      - generate_unbound_methods=true
+  - name: openapiv2
+    out: ./

gctrpc/buf.lock

@@ -0,0 +1,17 @@
+# Generated by buf. DO NOT EDIT.
+version: v1
+deps:
+  - remote: buf.build
+    owner: beta
+    repository: googleapis
+    branch: main
+    commit: 1c473ad9220a49bca9320f4cc690eba5
+    digest: b1-unlhrcI3tnJd0JEGuOb692LZ_tY_gCGq6mK1bgCn1Pg=
+    create_time: 2021-06-23T20:16:47.788079Z
+  - remote: buf.build
+    owner: grpc-ecosystem
+    repository: grpc-gateway
+    branch: main
+    commit: d19475fa22444a289c46af009acce62c
+    digest: b1-_zhDPyr_Ctc1QRAKuad6_0xvoyPd6QaB22ldm9gzS0Q=
+    create_time: 2021-04-26T15:19:26.742789Z

gctrpc/buf.yaml

@@ -0,0 +1,5 @@
+version: v1beta1
+name: buf.build/gocryptotrader/grpc
+deps:
+  - buf.build/beta/googleapis
+  - buf.build/grpc-ecosystem/grpc-gateway

go.mod

@@ -7,7 +7,6 @@ require (
 	github.com/d5/tengo/v2 v2.8.0
 	github.com/friendsofgo/errors v0.9.2 // indirect
 	github.com/gofrs/uuid v4.0.0+incompatible
-	github.com/golang/protobuf v1.5.2
 	github.com/google/go-querystring v1.1.0
 	github.com/gorilla/mux v1.8.0
 	github.com/gorilla/websocket v1.4.2