Applies_to: Expand versioning features

[cotti]

This PR provides a set of adjustments to the inner workings of versioning in the context of applies_to. This draft will be further updated with front-end changes, but badge-related changes can be checked independently.

It is part of #2135.

Problem description

Describing versions within applicability contains several quirks and limitations, such as:

• Lack of version range support: Authors can only specify single versions, making it difficult to document features that span multiple versions
• Patch-level badge overload: Showing full Major.Minor.Patch versions creates visual clutter, specially for more complex applicability scenarios
• Missing base version context: When no version is specified for versioned products, readers don't know they're viewing version-specific documentation (e.g., "Stack 9.0+")

Proposed changes

Version Specification (VersionSpec)

A new VersionSpec class has been created. It builds on SemVersion, and supports the following versioning types:

• Greater than or equal to: x.x+ or x.x (default)
• Range (inclusive): x.x-y.y
• Exact version: =x.x

// Examples:
stack: ga 9.1          // 9.1+ (default behavior)
stack: ga 9.1+         // 9.1+ (explicit)
stack: preview 9.0-9.2 // Range
stack: beta =9.1       // Exact version only

Simplified Badge Display

• Badges now display Major.Minor versions only, regardless of patch specification:
  9.5.0, 9.5.1, 9.5.6 -> all display as 9.5 or 9.5+

Base Version Display

When no version is specified for versioned products, the base version is now shown:

Before: stack: ga -> Badge shows just "Stack"
After: stack: ga -> Badge shows "Stack│8.0+" (assuming base = 8.0)

Unversioned products continue to show no version.

Validation Rules

Implemented validation in ApplicableToYamlConverter:

• One version declaration per lifecycle
• Only one "greater than or equal" per entry is allowed
• Ranges must not have a minimum version larger than the maximum version
• Overlapping version ranges are not allowed

# Valid:
stack: ga 9.2+, beta 9.0-9.1
stack: ga 9.2, beta =9.1

# Invalid - throws a warning:
stack: ga 9.2+, beta 9.0+     # Multiple >=
stack: ga 9.2+, beta 9.0-9.2  # Overlapping ranges

Tooltip -> Popover overhaul

The badge tooltip was replaced by a popover component.

[github-actions]

🔍 Preview links for changed docs

• docs/syntax/applies.md
• docs/testing/req.md

[reakaleek]

There are two test cases that made me curious.

Otherwise, LGTM.

Nice work.

[reakaleek]

➕ thanks for fixing this and making it properly.

[reakaleek]

I'm wondering a bit why there are so many warnings. What's the reason we can't do this backwards compatible?

[leemthompo]

[Maybe this isn't the right place to discuss this, so feel free to ignore...]

IMO the goal here is to display/explain the stack-versioning scheme, which applies to more products than this, so not sure if this is a helpful spot for this particular definition.

In the rendered part, I'd vote for removing "Stack" entirely and simply displaying the version.

For the Description, I'd say something like "Stack-versioned products and features follow the same semantic versioning scheme as Elasticsearch and Kibana."

[florent-leborgne]

Long debate on this one, we want to change this term soon. For now we'll stick with this, with the goal of explaining what "Stack" means to address some direct feedback. For the versioning model, we'll now always show a version in those badges, which should clarify a lot the intent of these badges wrt versioning

[leemthompo]

Fair enough, I'd insist, at least, that the current Description isn't super helpful in this context but 🤷

[benironside]

I love this update. Very excited to see version ranges coming to fruition, and I like the validation layer and the popover updates. Thank you!