Improve prefill in bank flows

[tillh-stripe]

Summary

This pull request adds PrefillDetails to ElementsSessionContext, which helps us prefill the form in the bank auth flow — both in the native and in the web flow.

This is irrespective of #9446, which is about the billing details we use when we construct the PaymentMethod object.

Motivation

Testing

• Added tests
• Modified tests
• Manually verified

Screenshots

Before	After
before screenshot	after screenshot

Changelog

[github-actions]

Diffuse output:

OLD: identity-example-release-base.apk (signature: V1, V2)
NEW: identity-example-release-pr.apk (signature: V1, V2)

          │          compressed          │         uncompressed         
          ├───────────┬───────────┬──────┼───────────┬───────────┬──────
 APK      │ old       │ new       │ diff │ old       │ new       │ diff 
──────────┼───────────┼───────────┼──────┼───────────┼───────────┼──────
      dex │     2 MiB │     2 MiB │  0 B │   4.1 MiB │   4.1 MiB │  0 B 
     arsc │     1 MiB │     1 MiB │  0 B │     1 MiB │     1 MiB │  0 B 
 manifest │   2.3 KiB │   2.3 KiB │  0 B │     8 KiB │     8 KiB │  0 B 
      res │ 301.8 KiB │ 301.8 KiB │  0 B │ 455.5 KiB │ 455.5 KiB │  0 B 
   native │   6.2 MiB │   6.2 MiB │  0 B │  15.8 MiB │  15.8 MiB │  0 B 
    asset │   7.1 KiB │   7.1 KiB │  0 B │   6.9 KiB │   6.9 KiB │  0 B 
    other │  90.2 KiB │  90.2 KiB │ +2 B │ 170.3 KiB │ 170.3 KiB │  0 B 
──────────┼───────────┼───────────┼──────┼───────────┼───────────┼──────
    total │   9.6 MiB │   9.6 MiB │ +2 B │  21.5 MiB │  21.5 MiB │  0 B 

 DEX     │ old   │ new   │ diff      
─────────┼───────┼───────┼───────────
   files │     1 │     1 │ 0         
 strings │ 19992 │ 19992 │ 0 (+0 -0) 
   types │  6203 │  6203 │ 0 (+0 -0) 
 classes │  4994 │  4994 │ 0 (+0 -0) 
 methods │ 29803 │ 29803 │ 0 (+0 -0) 
  fields │ 17570 │ 17570 │ 0 (+0 -0) 

 ARSC    │ old  │ new  │ diff 
─────────┼──────┼──────┼──────
 configs │  164 │  164 │  0   
 entries │ 3622 │ 3622 │  0

APK

   compressed    │   uncompressed   │                                           
──────────┬──────┼───────────┬──────┤                                           
 size     │ diff │ size      │ diff │ path                                      
──────────┼──────┼───────────┼──────┼───────────────────────────────────────────
 28.4 KiB │ +3 B │  62.9 KiB │  0 B │ ∆ META-INF/CERT.SF                        
  1.2 KiB │ -2 B │   1.2 KiB │  0 B │ ∆ META-INF/CERT.RSA                       
 25.3 KiB │ +2 B │  62.8 KiB │  0 B │ ∆ META-INF/MANIFEST.MF                    
    271 B │ -1 B │     120 B │  0 B │ ∆ META-INF/version-control-info.textproto 
──────────┼──────┼───────────┼──────┼───────────────────────────────────────────
 55.2 KiB │ +2 B │ 127.1 KiB │  0 B │ (total)

[tillh-stripe]

We don't need to focus the phone field if there’s already a value.

[tillh-stripe]

We want to fall back to any billing details that the merchant has passed in, even if it’s not being attached to the PaymentMethod.

[tillh-stripe]

Doing this outside of Instant Debits, as this also applies to the Networking flow.

[carlosmuvi-stripe]

👏

[carlosmuvi-stripe]

nit - we can likely inline this when adding query params (unless it makes them 2-liners)