[WIP] Mercadopago gateway implementation

[sgobotta]

This is a work in progress, do not merge.

Depends on coopcycle-web/pull/1655

Closes #729

Suggestion to repository maintainers:

• create a mercadopago branch from master
• edit the target branch of this PR
• delete this message afterwards

This PR provides:

• Basic checkout using react-native-mercadopago-px using a new component MercadopagoCheckout
• MoreInfo component refactor to choose between gateways

Pending tasks:

• Refactor the getPreferenceId function to an http call to the server. The preferences Mercadopago request should be done server-side
• Process the returned order from the server after the mercadopagoCheckout finishes
• Modify react-native-mercadopago-px usage to support split payments the auth/capture payment flow. This PR won't include such functionality

[alexsegura]

Why is this needed? Some people have quite old devices, see #745

[alexsegura]

Ok sorry, I didn't see the comment of 2373df7
I see, it appeared in version 4.29.0

[alexsegura]

Another possibility would be to override the version, like:

mercadoPagoPxVersion = "4.28.0"

But it doesn't seem like a good idea... @jamesdgrant are there lots of messengers with Android 4.3?

[sgobotta]

@alexsegura I'm fixing conflicts with master and encountered changes in the android build tools version. Are you probably using a newer gradle version? Here's some of the output:

> Task :app:processDebugManifest FAILED

Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/6.0.1/userguide/command_line_interface.html#sec:command_line_warnings
711 actionable tasks: 5 executed, 706 up-to-date

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:processDebugManifest'.
> java.lang.NullPointerException (no error message)

Current build tools versions:

buildToolsVersion = "29.0.2"
minSdkVersion = 19
compileSdkVersion = 29
targetSdkVersion = 29

Current gradle version:

Gradle 6.0.1

Run the restart script in README.md with no success. I'll be trying other versions, please let me know if you used any other specific configuration in the last master build

[sgobotta]

This PR depends on facttic/coopcycle-web@84d2593