docs(apid): Add apid docs

Describes apid and introduces some workflows to illustrate what apid does.

Signed-off-by: Brad Beam <brad.beam@talos-systems.com>

.conform.yaml

@@ -17,6 +17,7 @@ policies:
           - test
         scopes:
           - ami
+          - apid
           - ci
           - conformance
           - gpt

docs/website/content/v0.3.en.json

@@ -87,6 +87,10 @@
     "title": "Components",
     "path": "v0.3/en/components",
     "items": [
+      {
+        "title": "apid",
+        "path": "v0.3/en/components/apid"
+      },
       {
         "title": "kernel",
         "path": "v0.3/en/components/kernel"

docs/website/content/v0.3/en/components/apid.md

@@ -0,0 +1,49 @@
+---
+title: 'apid'
+---
+
+When interacting with Talos, the gRPC api endpoint you will interact with directly is `apid`.
+Apid acts as the gateway for all component interactions.
+Apid provides a mechanism to route requests to the appropriate destination when running on a control plane node.
+
+We'll use some examples below to illustrate what `apid` is doing.
+
+When a user wants to interact with a Talos component via `osctl`, there are two flags that control the interaction with `apid`.
+The `-e | --endpoints` flag is used to denote which Talos node ( via `apid` ) should handle the connection.
+Typically this is a public facing server.
+The `-n | --nodes` flag is used to denote which Talos node(s) should respond to the request.
+If `--nodes` is not specified, the first endpoint will be used.
+> Note: Typically there will be an `endpoint` already defined in the Talos config file.
+Optionally, `nodes` can be included here as well.
+
+For example, if a user wants to interact with `osd`, a command like `osctl -e cluster.talos.dev memory` may be used.
+
+```bash
+$ osctl -e cluster.talos.dev memory
+NODE                TOTAL   USED   FREE   SHARED   BUFFERS   CACHE   AVAILABLE
+cluster.talos.dev   7938    1768   2390   145      53        3724    6571
+```
+
+In this case, `osctl` is interacting with `apid` running on `cluster.talos.dev` and forwarding the request to the `osd` api.
+
+If we wanted to extend our example to retrieve `memory` from another node in our cluster, we could use the command `osctl -e cluster.talos.dev -n node02 memory`.
+
+```bash
+$ osctl -e cluster.talos.dev -n node02 memory
+NODE    TOTAL   USED   FREE   SHARED   BUFFERS   CACHE   AVAILABLE
+node02  7938    1768   2390   145      53        3724    6571
+```
+
+The `apid` instance on `cluster.talos.dev` receives the request and forwards it to `apid` running on `node02` which forwards the request to the `osd` api.
+
+We can further extend our example to retrieve `memory` for all nodes in our cluster by appending additional `-n node` flags or using a comma separated list of nodes ( `-n node01,node02,node03` ):
+
+```bash
+$ osctl -e cluster.talos.dev -n node01 -n node02 -n node03 memory
+NODE     TOTAL    USED    FREE     SHARED   BUFFERS   CACHE   AVAILABLE
+node01   7938     871     4071     137      49        2945    7042
+node02   257844   14408   190796   18138    49        52589   227492
+node03   257844   1830    255186   125      49        777     254556
+```
+
+The `apid` instance on `cluster.talos.dev` receives the request and forwards is to `node01`, `node02`, and `node03` which then forwards the request to their local `osd` api.