Update PNMessagingService.android.cs

[hajuuk]

Fix android:export compile issue #175.

[kirankumar4vr]

Can someone please review and merge this PR. This should fix the issue of deploying apps on Android 12. @rdelrosario -Thanks

[AndriyGlodan]

Hi guys! Please review this PR and approve it. This update is required to run Android apps using Target Android API 31. Because all new apps that will use this NuGet will not be available for publication.

Here is the official doc from Microsoft: https://developer.android.com/google/play/requirements/target-sdk#pre12

@rdelrosario, @Px7-941, @vikram-ma, @clintonrocksmith, @Char0394, @rdavisau, @zainniazi, @kpto

[Px7-941]

@AndriyGlodan I can't do the review until Monday. We are also in the process of Android 12 (SDK 31) migration.

[muhaym]

@Px7-941 / @rdelrosario (or any one with write access), how can we help to make the library support Android 12, Deadline is by November after which we'll not be able to publish newer version of app without targeting Android 12

[Px7-941]

@rdelrosario Can you merge the PR?

[Px7-941]

@muhaym here is a workaround

<application>
	<receiver android:name="com.google.firebase.iid.FirebaseInstanceIdInternalReceiver" android:exported="false" />
	<receiver android:name="com.google.firebase.iid.FirebaseInstanceIdReceiver" android:exported="true" android:permission="com.google.android.c2dm.permission.SEND">
		<intent-filter>
			<action android:name="com.google.android.c2dm.intent.RECEIVE" />
			<action android:name="com.google.android.c2dm.intent.REGISTRATION" />
			<category android:name="${applicationId}" />
		</intent-filter>
	</receiver>
	<service android:name="crc640921eac73192168e.PNMessagingService" android:exported="true" tools:node="merge">
		<intent-filter>
			<action android:name="com.google.firebase.MESSAGING_EVENT" />
		</intent-filter>
	</service>
</application>

you can add the missing export flags with the manifest merge solution.