feat: allow customizing monorepo references (#829)

* feat: allow customizing monorepo references

Instead of monorepo workspaces taking `string | TypeScriptWorkspace`,
they now take `string | IWorkspaceReference`.

A new method `customizeReference()` can be used to build an
`IWorkspaceReference` with non-default behavior. This adds 2 features:

- Allow public packages depending on private packages. This is not
  currently allowed, but makes sense if we are bundling the target
  package.
- Allow customizing the generated version range. We default to
  `^`, but that may not be desired. Sometimes we want the exact
  version.

* chore: self mutation

Signed-off-by: github-actions <[email protected]>

* Make it a project-wide option

---------

Signed-off-by: github-actions <[email protected]>
Co-authored-by: github-actions <[email protected]>

Author: rix0rrr

API.md

@@ -141,7 +141,7 @@ export function generateYarnMonorepoOptions(project: typescript.TypeScriptProjec
         union: {
           types: [
             { primitive: PrimitiveType.String },
-            { fqn: 'cdklabs-projen-project-types.yarn.TypeScriptWorkspace' },
+            { fqn: 'cdklabs-projen-project-types.yarn.IWorkspaceReference' },
           ],
         },
       },
@@ -231,6 +231,20 @@ export function generateYarnMonorepoOptions(project: typescript.TypeScriptProjec
           default: '\'lts/*\'',
         },
       },
+      {
+        name: 'allowPrivateDeps',
+        optional: true,
+        type: { primitive: PrimitiveType.Boolean },
+        docs: {
+          summary: [
+            'Allow private workspace dependencies in the \'deps\' parameter.',
+            '',
+            'By default, private dependencies are not allowed as users will not be able to install',
+            'your package. It makes sense to relax this check *only* if you are bundling your package.',
+          ].join('\n'),
+          default: 'false',
+        },
+      },
     ],
   });