fix(module-federation): disallow imported fallback modules in mf

Signed-off-by: Carl-Erik Bergström <cbergstrom@spotify.com>

.changeset/angry-heads-design.md

@@ -0,0 +1,5 @@
+---
+'@backstage/cli': patch
+---
+
+Disallow import fallback of critical shared dependencies in module federation.

packages/cli/src/modules/build/lib/bundler/config.ts

@@ -264,24 +264,30 @@ export async function createConfig(
             singleton: true,
             requiredVersion: '*',
             eager: !isRemote,
+            import: false,
           },
           'react-dom': {
             singleton: true,
             requiredVersion: '*',
             eager: !isRemote,
+            import: false,
           },
           // React Router
           'react-router': {
             singleton: true,
             requiredVersion: '*',
             eager: !isRemote,
+            import: false,
           },
           'react-router-dom': {
             singleton: true,
             requiredVersion: '*',
             eager: !isRemote,
+            import: false,
           },
           // MUI v4
+          // not setting import: false for MUI packages as this
+          // will break once Backstage moves to BUI
           '@material-ui/core/styles': {
             singleton: true,
             requiredVersion: '*',
@@ -293,6 +299,8 @@ export async function createConfig(
             eager: !isRemote,
           },
           // MUI v5
+          // not setting import: false for MUI packages as this
+          // will break once Backstage moves to BUI
           '@mui/material/styles/': {
             singleton: true,
             requiredVersion: '*',