[jfrosorio]

Closes #106.

The channel setting fell back to demo when EUPAGO_CHANNEL was unset. Since every callback is rejected unless its channel matches the setting, an app that forgot the variable booted normally and silently confirmed no payment.

• config/eupago.php no longer has a fallback for channel.
• A new CodeTech\EuPago\Exceptions\MissingConfiguration exception is thrown by CallbackRequest when a callback arrives while the channel or the API key is blank, instead of the callback being rejected as forged.
• UPGRADE.md has a v3.11.0 entry for apps that relied on the demo fallback or published the config; README and docs/configuration.md / docs/callbacks.md describe the new behaviour.
• Feature tests cover the exception for both blank settings.

[Copilot]

🟢 Approval recommended

The change replaces a risky silent demo fallback with an explicit missing-configuration exception during callbacks, updates documentation accordingly, and adds feature tests covering the new failure behavior without noting any outstanding issues.

No open issues 🎉

What changed in this PR

This PR removes the implicit demo default for the channel configuration to prevent production apps from silently rejecting all payment callbacks when EUPAGO_CHANNEL is missing, and instead makes missing callback-critical configuration fail loudly via a dedicated exception.

Changes:

• Remove the demo fallback for config('eupago.channel') and document the new “no default” behavior.
• Throw CodeTech\EuPago\Exceptions\MissingConfiguration when a callback arrives while eupago.channel or eupago.api_key is blank.
• Add feature coverage ensuring callbacks surface missing configuration as an exception.

File	Description
config/​eupago.php	Drops the demo fallback for channel and documents the rationale directly in the config comments.
src/​Http/​Requests/​CallbackRequest.php	Adds a pre-validation guard that throws on blank channel/api_key during callbacks.
src/​Exceptions/​MissingConfiguration.php	Introduces a dedicated exception for missing/blank required settings during callback handling.
tests/​Feature/​CallbackTest.php	Adds feature coverage asserting missing config is reported via MissingConfiguration rather than a forged-callback rejection.
tests/​Feature/​PackageBootTest.php	Updates boot/merge expectations to no longer rely on a demo channel default.
UPGRADE.md	Documents the breaking behavior change and how to migrate apps that relied on the implicit demo fallback.
README.md	Clarifies that the configured channel must match the backoffice channel name exactly.
docs/​configuration.md	Explains that neither EUPAGO_CHANNEL nor EUPAGO_API_KEY has a default and that missing values surface via exception on callback.
docs/​callbacks.md	Documents the new exception behavior when callback-critical settings are blank.

_{Review effort: Lite}