[cmd/mdatagen] add unsupported platforms to the README header (#9803)

**Description:**
Add unsupported platforms to the README header

**Link to tracking Issue:**
Fixes #9794

.chloggen/add_unsupported_platforms.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: mdatagen
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Adds unsupported platforms to the README header
+
+# One or more tracking issues or pull requests related to the change
+issues: [9794]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

.github/workflows/check_links_config.json

@@ -8,6 +8,9 @@
         },
         {
             "pattern": "http(s)?://example.com"
+        },
+        {
+            "pattern": "#warnings"
         }
     ],
     "aliveStatusCodes": [429, 200],

cmd/mdatagen/internal/samplereceiver/README.md

@@ -0,0 +1,22 @@
+# Sample Receiver
+This receiver is used for testing purposes to check the output of mdatagen.
+<!-- status autogenerated section -->
+| Status        |           |
+| ------------- |-----------|
+| Stability     | [development]: logs   |
+|               | [beta]: traces   |
+|               | [stable]: metrics   |
+| Unsupported Platforms | freebsd, illumos |
+| Distributions | [] |
+| Warnings      | [Any additional information that should be brought to the consumer's attention](#warnings) |
+| Issues        | [![Open issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aopen%20label%3Areceiver%2Fsample%20&label=open&color=orange&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Areceiver%2Fsample) [![Closed issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aclosed%20label%3Areceiver%2Fsample%20&label=closed&color=blue&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aclosed+is%3Aissue+label%3Areceiver%2Fsample) |
+| [Code Owners](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#becoming-a-code-owner)    | [@dmitryax](https://www.github.com/dmitryax) |
+
+[development]: https://github.com/open-telemetry/opentelemetry-collector#development
+[beta]: https://github.com/open-telemetry/opentelemetry-collector#beta
+[stable]: https://github.com/open-telemetry/opentelemetry-collector#stable
+<!-- end autogenerated section -->
+
+## Warnings
+
+This is where warnings are described.

cmd/mdatagen/internal/samplereceiver/generated_component_test.go

@@ -1,4 +1,5 @@
 // Code generated by mdatagen. DO NOT EDIT.
+//go:build !freebsd && !illumos
 
 package samplereceiver
 

cmd/mdatagen/internal/samplereceiver/metadata.yaml

@@ -12,6 +12,7 @@ status:
     beta: [traces]
     stable: [metrics]
   distributions: []
+  unsupported_platforms: [freebsd, illumos]
   codeowners:
     active: [dmitryax]
   warnings:

cmd/mdatagen/loader_test.go

@@ -36,6 +36,7 @@ func TestLoadMetadata(t *testing.T) {
 						Active: []string{"dmitryax"},
 					},
 					Warnings:             []string{"Any additional information that should be brought to the consumer's attention"},
+					UnsupportedPlatforms: []string{"freebsd", "illumos"},
 				},
 				ResourceAttributes: map[attributeName]attribute{
 					"string.resource.attr": {

cmd/mdatagen/templates/readme.md.tmpl

@@ -11,6 +11,9 @@
 {{- $idx = inc $idx }}
 {{- end }}
 {{- end}}
+{{- if .Status.UnsupportedPlatforms }}
+| Unsupported Platforms | {{ stringsJoin .Status.UnsupportedPlatforms ", " }} |
+{{- end }}
 {{- if and (ne $class "cmd") (ne $class "pkg")  }}
 | Distributions | [{{ stringsJoin .Status.SortedDistributions "], [" }}] |
 {{- end }}