Merge pull request #15801 from backstage/mob/bs-docs

docs: introduce initial backend system documentation structure

microsite/sidebars.json

@@ -239,8 +239,7 @@
           "plugins/proxying",
           "plugins/backend-plugin",
           "plugins/call-existing-api",
-          "plugins/url-reader",
-          "plugins/new-backend-system"
+          "plugins/url-reader"
         ]
       },
       {
@@ -363,6 +362,46 @@
       "architecture-decisions/adrs-adr012",
       "architecture-decisions/adrs-adr013"
     ],
-    "FAQ": ["FAQ"]
+    "FAQ": ["FAQ"],
+    "Experimental Backend System": [
+      {
+        "_hidden_": [
+          "backend-system/index",
+          {
+            "type": "subcategory",
+            "label": "Architecture",
+            "ids": [
+              "backend-system/architecture/index",
+              "backend-system/architecture/services",
+              "backend-system/architecture/plugins",
+              "backend-system/architecture/extension-points",
+              "backend-system/architecture/modules"
+            ]
+          },
+          {
+            "type": "subcategory",
+            "label": "Building Backends",
+            "ids": [
+              "backend-system/building-backends/index",
+              "backend-system/building-backends/migrating"
+            ]
+          },
+          {
+            "type": "subcategory",
+            "label": "Building Plugins & Modules",
+            "ids": [
+              "backend-system/building-plugins-and-modules/index",
+              "backend-system/building-plugins-and-modules/testing",
+              "backend-system/building-plugins-and-modules/migrating"
+            ]
+          },
+          {
+            "type": "subcategory",
+            "label": "Core Services",
+            "ids": ["backend-system/core-services/index"]
+          }
+        ]
+      }
+    ]
   }
 }