refactor(v2): remove sidebar_label filed from doc metadata file

[lex111]

Motivation

After merging #4495, all frontmatter fields became part of doc metadata, we have at least one redundant field -- sidebar_label. We can safely remove it from the current metadata, and get it from the frontMatter field instead.

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Test Plan

Tests passed.

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[lex111]

I also noticed the slug field, which seems to come from frontmatter (?), maybe we should also remove it as a separate field from the doc metadata?

In general, are all fields in doc metadata currently used, perhaps we should remove or somehow reduce them?

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[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	64
🟢 Accessibility	97
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

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✔️ [V1]

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[github-actions]

Size Change: 0 B

Total Size: 620 kB

ℹ️ View Unchanged

Filename	Size	Change
website/build/assets/css/styles.********.css	88.1 kB	0 B
website/build/assets/js/main.********.js	443 kB	0 B
website/build/blog/2017/12/14/introducing-docusaurus/index.html	62.1 kB	0 B
website/build/docs/introduction/index.html	235 B	0 B
website/build/index.html	26.9 kB	0 B

_{compressed-size-action}

[slorber]

That makes sense thanks!

---

For the slug, the metadata.slug is not exactly the same as frontMatter.slug (cf getSlug()).

frontmatter slug is optional, but metadata slug is always present and computed using the frontmatter slug

It seems only used in getMainDoc() to test for `doc.slug === '/'

I think we should keep it because we should add better support for docs/index.md => it should have metadata.slug = '/' despite not having explicit frontMatter.slug = '/', and be considered the "home" of a version.

My idea of how this should work to make it easy to understand and maintain:

• we keep frontmatter 100% untouched
• when we have to do some computations based on multiple variables (including frontmatter, filenames etc), we compute this once and put it in the doc metadata, so that it can be used in one or more places later without risking to duplicate this computation logic
• if a metadata value exist, it's better to read it there than on the frontmatter.

sidebar_label can be safely removed from metadata because we don't do any computation on it, so it's always the same value as the frontmatter value, and it's safe to read from the frontmatter directly