Fix misleading Community Build upgrade error message

[mishaTsukini]

Summary

• MIN_UPGRADE_VERSION is set to 2026_01_000 (the first migration of version 26.1)
• However, MIN_UPGRADE_VERSION_COMMUNITY_BUILD_READABLE was set to "25.12"
• This causes users upgrading from 25.12 to see: "Please upgrade to the 25.12 version first" — even though they are already on 25.12
• The fix changes the readable constant to "26.1" to match the actual numeric requirement

Context

When upgrading SonarQube Community Build from 25.12 (last migration 2025_06_026 = 202506026) to any version >= 26.3 (which requires MIN_UPGRADE_VERSION = 2026_01_000 = 202601000), the error message tells the user to upgrade to 25.12 first. This is confusing and incorrect — the user needs to upgrade to 26.1 first so that migration 2026_01_000 gets applied.

The Server Edition message (MIN_UPGRADE_VERSION_HUMAN_READABLE = "2026.1") is already correct. Only the Community Build message was wrong.

How to reproduce

1. Set up SonarQube Community Build 25.12 with a fully migrated database (max schema_migrations = 202506026)
2. Attempt to start SonarQube 26.4 against the same database
3. Observe error: "Please upgrade to the 25.12 version first"
4. Expected: "Please upgrade to the 26.1 version first"

Test plan

• Updated DatabaseServerCompatibilityTest.fail_if_requires_firstly_to_upgrade_to_26_1 to verify the corrected message

[sonar-review-alpha]

Summary

This PR corrects a constant mismatch in Community Build upgrade validation. The MIN_UPGRADE_VERSION numeric value requires version 26.1 (migration 2026_01_000), but the user-facing message constant was set to "25.12", causing users already on 25.12 to see a confusing error telling them to upgrade to 25.12 first.

The fix changes MIN_UPGRADE_VERSION_COMMUNITY_BUILD_READABLE from "25.12" to "26.1" to match the actual requirement, and updates the corresponding test to verify the corrected message.

What reviewers should know

Validation points:

• The numeric constant MIN_UPGRADE_VERSION = 2026_01_000 (unchanged) represents the database schema version required
• The readable constant now aligns with this requirement (26.1 is the version that applies this migration)
• Compare this to MIN_UPGRADE_VERSION_HUMAN_READABLE = "2026.1" in the same file—it matches exactly
• Test name and expected message both updated consistently

Where to look:

• DatabaseVersion.java line 38: the single constant fix
• DatabaseServerCompatibilityTest.java lines 72 and 79: the test that validates Community Build error messages

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[sonar-review-alpha]

Clean, minimal fix. The constant change is correct and the test verifies the full message string end-to-end.

🗣️ Give feedback

[sonar-review-alpha]

The comment on line 36 (// In reality user is required to upgrade just to 10.8 but we want to 'market' 2025.1) is stale — it refers to version numbers unrelated to the current constants (26.1 / 2026.1). This PR touches these lines, so it's a good opportunity to update or remove it.

Suggested change

	// In reality user is required to upgrade just to 10.8 but we want to 'market' 2025.1
	public static final String MIN_UPGRADE_VERSION_HUMAN_READABLE = "2026.1";
	public static final String MIN_UPGRADE_VERSION_HUMAN_READABLE = "2026.1";
	public static final String MIN_UPGRADE_VERSION_COMMUNITY_BUILD_READABLE = "26.1";

• Mark as noise