PIMOB: 5473 - Bump checkoutAndroidComponents to 2.8.0 and add msc+rm support

[chintan-soni-cko]

Bumps the sample app to checkout-android-components 2.8.0 and wires end-to-end support for Merchant Saved Card + Remember Me (MSC+RM) so the blended experience can be exercised from the sample app. Also reworks the session customer setup so identifiers (email/phone) are only sent when explicitly provided.

Issue

PIMOB-5473

Proposed changes

Stored Card (MSC+RM)

• Bump checkoutAndroidComponents 2.6.1 → 2.8.0.
• New StoredCardSettings state, gated on a single source of truth: enabled = customerId.isNotBlank() (no separate toggle — presence of a Customer ID is what turns the feature on).
• New collapsible Stored Card Configurations settings section: Customer ID, Display mode (friendly "Default only" / "All" labels), Capture CVV, accepted schemes/types.
• Session request: when a Customer ID is present, stored_card is added to enabled_payment_methods and payment_method_configuration.stored_card.customer_id is sent (new serializable wire models). Component config builds a StoredCardConfiguration into ComponentOption.
• Guard-off = untouched: a blank Customer ID leaves both the session and component configuration unmodified.

Payment session customer setup

• New collapsible Payment Session Setup section grouping Address Country, Customer Email, and Customer Phone Number (phone dialing code derived from the country).
• Customer email/phone are now nullable and only sent when non-blank; explicitNulls = false omits unset keys from the request.
• Removed the hard-coded billing/shipping phone (1234567890) — no phone is sent unless provided.
• Region presets no longer inject hard-coded emails/phones, so cleared values stay cleared.

Test Steps

1. Open Settings → Payment Session Setup: with Email and Phone blank, start a flow and confirm the session carries no customer email/phone (so Remember Me has no identifier to resolve).
2. Enter a Customer Email and/or Phone, start a flow again, and confirm the provided identifier(s) are sent.
3. Open Settings → Stored Card Configurations, enter a Customer ID with saved cards, optionally adjust Display mode / Capture CVV / schemes / types, and start a flow to verify saved cards are presented per the configuration.
4. Clear the Customer ID and verify the stored card feature is fully off (session and component unchanged).

testing video

Checklist

• Reviewers assigned
• I have performed a self-review of my code and manual testing
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if applicable)

Further comments

Stored card is gated on Customer ID presence rather than a dedicated toggle, since the session's customer_id is the real driver for resolving saved cards. The customer email/phone rework makes it possible to validate the "no identifier" path, which previously always triggered Remember Me because a phone was hard-coded onto the session.

[Copilot]

Copilot review overview

🟡 Changes recommended

Stale Compose callbacks can reset settings, and asynchronous state reads can produce inconsistent session and component configurations.

Review effort: Balanced
Findings: 2 · 1

Open (3)

• Use one stored-card settings snapshot for session and component configuration · New
• Avoid stale stored-card settings in SampleOutlineTextField callback · New
• Document the new storedCardSettings KDoc parameter · New

What changed in this PR

Adds merchant-stored-card configuration to the sample checkout flow and upgrades Checkout Android Components to 2.8.0.

Changes:

• Adds stored-card session and component configuration.
• Adds stored-card settings UI and state.
• Updates the sample dependency and default customer email.

File	Description
sample/​gradle/​libs.versions.toml	Upgrades components to 2.8.0.
PaymentSessions.kt	Adds stored-card request models.
strings.xml	Adds stored-card labels.
SettingsScreen.kt	Adds stored-card settings controls.
StoredCardSettings.kt	Defines stored-card UI state.
Settings.kt	Updates the default email.
Constants.kt	Exposes display-mode options.
DemoScreen.kt	Wires stored-card state into settings.
MainViewModel.kt	Builds stored-card component options.
MainActivity.kt	Connects stored-card state and updates.
FlowComponent.kt	Configures stored-card payment sessions.
Extensions.kt	Adds display-mode labels.

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