fix(techdocsStorageClient): properly construct baseUrls

[kuangp]

Signed-off-by: Phil Kuang pkuang@factset.com

Hey, I just made a Pull Request!

Context: mkdocs/mkdocs#2456

We have some docs with the older style of relative links as shown in the linked issue above.
eg. [linking to other page](../foo-bar) which loads /docs/default/Component/my-component/foo-bar (note the missing trailing slash)

Looking into the TechDocs reader, this is inherently supported when attempting to load the raw docs html and inspecting the network requests, it is being fetched correctly since the trailing slash is added appropriately:

backstage/plugins/techdocs/src/client.ts

Lines 162 to 174 in a173851

	async getEntityDocs(entityId: EntityName, path: string): Promise<string> {
	const { kind, namespace, name } = entityId;
	const storageUrl = await this.getStorageUrl();
	const url = `${storageUrl}/${namespace}/${kind}/${name}/${path}`;
	const token = await this.identityApi.getIdToken();
	const request = await fetch(
	`${url.endsWith('/') ? url : `${url}/`}index.html`,
	{
	headers: token ? { Authorization: `Bearer ${token}` } : {},
	},
	);

The issue arises when updating links that load additional assets:

backstage/plugins/techdocs/src/reader/transformers/addBaseUrl.ts

Lines 60 to 64 in a173851

	const newValue = await techdocsStorageApi.getBaseUrl(
	elemAttribute,
	entityId,
	path,
	);

eg. a <link href="../extra.css"> is incorrectly transformed to <link href="<app-origin>/static/docs/default/Component/extra.css" />

This change fixes the URL transformation to ensure a trailing slash so that the asset path is resolved correctly eg. <link href="<app-origin>/static/docs/default/Component/my-component/extra.css" />

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[changeset-bot]

🦋 Changeset detected

Latest commit: e7cce2b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@backstage/plugin-techdocs	Patch

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[github-actions]

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[kuangp]

@iamEAP can you take a look at this change when you get a chance please ?

[OrkoHunter]

Hey @kuangp ! Eric is on vacation as of now - please be patient as someone in @backstage/techdocs-core can take a look! 🙏

Although this looks good to me - @emmaindal thoughts?

[emmaindal]

Sorry @kuangp I did look at this last week, just didn't approve 😄 Can you prefix the changeset with techdocs-*

[kuangp]

thanks @emmaindal ! updated the changeset