docs(global-header): add initial tech docs (#413)

Signed-off-by: Christoph Jerolimov <jerolimov+git@redhat.com>

Author: christoph-jerolimov

workspaces/global-header/app-config.yaml

@@ -99,15 +99,14 @@ catalog:
   locations:
     # Local example data, file locations are relative to the backend process, typically `packages/backend`
     - type: file
-      target: ../../examples/entities.yaml
+      target: ../../catalog-info.yaml
 
-    # Local example template
+    - type: file
+      target: ../../examples/entities.yaml
     - type: file
       target: ../../examples/template/template.yaml
       rules:
         - allow: [Template]
-
-    # Local example organizational data
     - type: file
       target: ../../examples/org.yaml
       rules:

workspaces/global-header/catalog-info.yaml

@@ -5,6 +5,7 @@ metadata:
   title: RHDH Global Header plugin
   description: The global header plugins provides an extendable way for the RHDH header. It provides a set of default components and also allow other plugins can contribute components to the header.
   annotations:
+    backstage.io/techdocs-ref: dir:.
     github.com/project-slug: redhat-developer/rhdh-plugins
     github.com/team-slug: redhat-developer/rhdh-plugins-contributers
     #sonarqube.org/project-key: redhat-developer_rhdh-plugins
@@ -14,7 +15,7 @@ metadata:
     - plugin
 spec:
   type: backstage-plugin
-  lifecycle: development
+  lifecycle: production
   owner: rhdh-ui-team
   system: rhdh
   subcomponentOf: rhdh-plugins

workspaces/global-header/docs/index.md

@@ -0,0 +1,8 @@
+# Global header
+
+Red Hat Developer Hub includes a new configable and highly extendable global header plugin starting with RHDH 1.5.
+
+By default it includes a Search input field, Create, Support[^1] and Notifications[^2] icon buttons and a user profile dropdown.
+
+[^1]: Only when the Support URL is configured in the `app-config.yaml`.
+[^2]: Only when the notification plugin is installed.

workspaces/global-header/mkdocs.yaml

@@ -0,0 +1,7 @@
+site_name: RHDH Global Header
+
+plugins:
+  - techdocs-core
+
+nav:
+  - About: index.md

workspaces/global-header/plugins/global-header/dev/configuration.md

@@ -0,0 +1,50 @@
+# Configuration
+
+The Red Hat Developer Hub Global Header can be configured via [dynamic plugins](https://github.com/redhat-developer/rhdh/blob/main/docs/dynamic-plugins/index.md) and [dynamic plugin mount points](https://github.com/redhat-developer/rhdh/blob/main/docs/dynamic-plugins/frontend-plugin-wiring.md).
+
+It is the RHDH default "[application header](https://github.com/redhat-developer/rhdh/blob/main/docs/dynamic-plugins/frontend-plugin-wiring.md#adding-application-header)" implementation that customers can extend or replace.
+
+There are multiple level of extension points (mount points) involved.
+
+1. Red Hat Developer Hub loads all "application headers"
+2. The Global Header plugin is loaded by default (it's of only header implementation)
+   - The header itself can be extended with additional buttons, dropdowns via dynamic plugins
+   - Also the Create and Profile Dropdowns can be extended with additional options
+
+## Disabling the Global Header
+
+The RHDH Global Header can be disabled competely by disabling the right plugin:
+
+```yaml
+# Disabling global header
+- package: ./dynamic-plugins/dist/red-hat-developer-hub-backstage-plugin-global-header
+  disabled: true
+```
+
+## Replacing the Global Header with your own header
+
+To replace the RHDH Global Header with a completly custom header, the default should be disabled as well (see above).
+
+After that customers can implement and install their own header as a dynamic plugin and include a configuration like this:
+
+```yaml
+# Custom header implementation
+- package: <npm or oci package-reference>
+  disabled: false
+  pluginConfig:
+    dynamicPlugins:
+      frontend:
+        <package_name>:
+          mountPoints:
+            - mountPoint: application/header
+              importName: <Header component name>
+              config:
+                layout:
+                  position: above-main-content
+```
+
+<!--
+## Disable Global Header features
+
+## Add custom components to the Global Header
+-->