docs: extend client generation with buf (#5662)

docs/docs/examples/sdks.md

@@ -13,6 +13,71 @@ title: SDKs
 | Python   | 🚧 [WIP](https://github.com/zitadel/zitadel/issues/3675) | ❓ | ❓ | TBD |
 | NodeJS   | [@zitadel/node](https://www.npmjs.com/package/@zitadel/node) | ❌ | ✔️ | `community` |
 
+## Missing an SDK
+
+Is your language/framework missing? Fear not, you can generate your gRPC API Client with ease.
+
+1. Make sure to install [buf](https://buf.build/docs/installation/)
+2. Create a `buf.gen.yaml` and configure the [plugins](https://buf.build/plugins) you need
+3. Run `buf generate https://github.com/zitadel/zitadel#format=git,tag=v2.23.1` (change the versions to your needs)
+
+Let us make an example with Ruby. Any other supported language by buf will work as well. Consult the [buf plugin registry](https://buf.build/plugins) for more ideas.
+
+### Example with Ruby
+
+With gRPC we usually need to generate the client stub and the messages/types. This is why we need two plugins.
+The plugin `grpc/ruby` generates the client stub and the plugin `protocolbuffers/ruby` takes care of the messages/types.
+
+```yaml
+version: v1
+plugins:
+  - plugin: buf.build/grpc/ruby
+    out: gen
+  - plugin: buf.build/protocolbuffers/ruby
+    out: gen
+```
+
+If you now run `buf generate https://github.com/zitadel/zitadel#format=git,tag=v2.23.1` in the folder where your `buf.gen.yaml` is located you should see the folder `gen` appear.
+
+If you run `ls -la gen/zitadel/` you should see something like this:
+
+```bash
+ffo@ffo-pc:~/git/zitadel/ruby$ ls -la gen/zitadel/
+total 704
+drwxr-xr-x 2 ffo ffo   4096 Apr 11 16:49 .
+drwxr-xr-x 3 ffo ffo   4096 Apr 11 16:49 ..
+-rw-r--r-- 1 ffo ffo   4397 Apr 11 16:49 action_pb.rb
+-rw-r--r-- 1 ffo ffo 141097 Apr 11 16:49 admin_pb.rb
+-rw-r--r-- 1 ffo ffo  25151 Apr 11 16:49 admin_services_pb.rb
+-rw-r--r-- 1 ffo ffo   6537 Apr 11 16:49 app_pb.rb
+-rw-r--r-- 1 ffo ffo   1134 Apr 11 16:49 auth_n_key_pb.rb
+-rw-r--r-- 1 ffo ffo  32881 Apr 11 16:49 auth_pb.rb
+-rw-r--r-- 1 ffo ffo   6896 Apr 11 16:49 auth_services_pb.rb
+-rw-r--r-- 1 ffo ffo   1571 Apr 11 16:49 change_pb.rb
+-rw-r--r-- 1 ffo ffo   2488 Apr 11 16:49 event_pb.rb
+-rw-r--r-- 1 ffo ffo  14782 Apr 11 16:49 idp_pb.rb
+-rw-r--r-- 1 ffo ffo   5031 Apr 11 16:49 instance_pb.rb
+-rw-r--r-- 1 ffo ffo 223348 Apr 11 16:49 management_pb.rb
+-rw-r--r-- 1 ffo ffo  44402 Apr 11 16:49 management_services_pb.rb
+-rw-r--r-- 1 ffo ffo   3020 Apr 11 16:49 member_pb.rb
+-rw-r--r-- 1 ffo ffo    855 Apr 11 16:49 message_pb.rb
+-rw-r--r-- 1 ffo ffo   1445 Apr 11 16:49 metadata_pb.rb
+-rw-r--r-- 1 ffo ffo   2370 Apr 11 16:49 object_pb.rb
+-rw-r--r-- 1 ffo ffo    621 Apr 11 16:49 options_pb.rb
+-rw-r--r-- 1 ffo ffo   4425 Apr 11 16:49 org_pb.rb
+-rw-r--r-- 1 ffo ffo   8538 Apr 11 16:49 policy_pb.rb
+-rw-r--r-- 1 ffo ffo   8223 Apr 11 16:49 project_pb.rb
+-rw-r--r-- 1 ffo ffo   1022 Apr 11 16:49 quota_pb.rb
+-rw-r--r-- 1 ffo ffo   5872 Apr 11 16:49 settings_pb.rb
+-rw-r--r-- 1 ffo ffo  20985 Apr 11 16:49 system_pb.rb
+-rw-r--r-- 1 ffo ffo   4784 Apr 11 16:49 system_services_pb.rb
+-rw-r--r-- 1 ffo ffo  28759 Apr 11 16:49 text_pb.rb
+-rw-r--r-- 1 ffo ffo  24170 Apr 11 16:49 user_pb.rb
+-rw-r--r-- 1 ffo ffo  13568 Apr 11 16:49 v1_pb.rb
+```
+
+Import these files into your project to start interacting with ZITADEL's APIs.
+
 ## More
 
 While we are not actively maintaining the following projects, it is worth checking out if you're interested in exploring ZITADEL in different programming languages or frameworks.