TechDocs: Use lowercase entity kind, namespace and name in URLs

Feature Suggestion

When you open a TechDocs page like https://demo.backstage.io/docs/default/Component/backstage

The entity namespace (e.g. default) and kind (e.g. Component) and name should be in lowercase.

Possible Implementation

Look at /catalog plugin for inspiration.

https://github.com/backstage/backstage/blob/8e1c7be11c916d95e9281914b98c59a79d0a1ada/plugins/catalog-react/src/routes.ts#L39-L46

[iamEAP]

We took a look at this and here’s our proposed path forward…

1. Create a migration utility (most likely a command in techdocs-cli) that will copy any objects in storage from case-sensitive triplet paths to lower-case triplet paths.
2. This migration utility will rely on a new method added to the PublisherBase signature (perhaps called migrateDocsCase or similar) which handles the logic on a per-storage provider basis. (We may want to publish this in TechDocs common, followed by the techdocs-cli first, to allow time to advertise the change to the community and resolve any issues in the migration command)
3. We’ll then update all publishers’ publish and docsRouter methods to lowercase the entity triplet at read/write time. In the release notes in this PR, we’ll advise those who use external storage/generation solutions to run the techdocs-cli migration command prior to rolling out the release. (As noted previously in this issue, folks running local generation will be unaffected)

One additional annoyance: MacOS’s file system is case insensitive by default, so testing this locally on a Mac is challenging.

[adamdmharvey]

Closure of this potentially also closes https://github.com/backstage/backstage/issues/2269