fix(singular): raise singular-12 sample app minSdk to 21

[jamesnrokt]

What

One line — the singular-12 Kotlin sample app's minSdk goes from 16 to 21.

 kits/singular/singular-12/example/example-kotlin/build.gradle
     applicationId 'com.mparticle.kits.singular.example.kotlin'
-    minSdk 16
+    minSdk 21

Why

build-kits / Build singular-12 has failed on every PR since 2026-07-23 with no code change on our side — it currently blocks #742, #743, #744 and #722.

The kit declares Singular with an open version range, so 12.15.0 was picked up automatically. That release raised its own minSdk to 21:

Manifest merger failed : uses-sdk:minSdkVersion 16 cannot be smaller than
version 21 declared in library [com.singular.sdk:singular_sdk:12.15.0]

Manifest merger enforces minSdk compatibility only for application modules; library modules downgrade it to a warning. The sample app is the sole application module in this kit, so it is the only thing that can fail.

Scope: sample app only

The job runs three Gradle steps. Steps 1–2 already pass; only step 3 fails:

#	Step	Result
1	publishMavenPublicationToMavenLocal	✅
2	singular-12:testRelease	✅
3	example-kotlin:assembleDebug	❌ the failure

No externally visible change

• Sample apps are not published.
• The kit keeps minSdkVersion 16 — untouched.
• The Singular version range is untouched.

Verified the publishable artifact is unaffected:

> Task :kits:singular:singular-12:processReleaseManifest
> Task :kits:singular:singular-12:bundleReleaseAar
BUILD SUCCESSFUL

Verification

Reproduced the CI steps locally (JDK 17), using --rerun-tasks to rule out Gradle caching:

Config	processDebugMainManifest
minSdk 21 (this PR)	✅ BUILD SUCCESSFUL
minSdk 16 (control)	❌ reproduces the exact CI error

Reviewer note

A customer on minSdk 16–20 who adds singular-12 will hit this same manifest merger error in their own build, because Singular is an api dependency and therefore transitive in the published POM.

This PR deliberately does not raise the published kit's minSdk — that is a breaking change and warrants its own decision. Flagging so it is tracked rather than forgotten.

🤖 Generated with Claude Code

[cursor]

PR Summary

Low Risk
Sample-only Gradle change with no published artifact or kit minSdk change.

Overview
Raises minSdk from 16 to 21 in the singular-12 Kotlin example app (example-kotlin/build.gradle) so assembleDebug passes manifest merger after Singular SDK 12.15.0 requires minSdk 21.

The published singular-12 kit still declares minSdkVersion 16; only the non-published sample app changes.

^{Reviewed by Cursor Bugbot for commit a4d5dca. Bugbot is set up for automated code reviews on this repo. Configure here.}

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud