feat(functions): replace FunctionRegion enum with open struct

[grdsdev]

Summary

Backports the FunctionRegion type change from release/v3 (part of 02b45208).

What changed: public enum FunctionRegion: String → public struct FunctionRegion: RawRepresentable, Hashable, Sendable with ExpressibleByStringLiteral.

Why: The enum locks users to the 14 hardcoded regions. The struct allows custom values for regions not yet in the SDK:

// new — custom region
options.region = FunctionRegion(rawValue: "custom-region")
options.region = "custom-region"  // via ExpressibleByStringLiteral

// existing — unchanged, still works
options.region = .usEast1
options.region = .caCentral1
let raw = options.region?.rawValue  // still compiles

Migration

No change needed for the vast majority of code — .usEast1, .caCentral1 etc. keep their names, rawValue is unchanged, and FunctionRegion? parameters still accept the same values.

One source-breaking case: exhaustive switch statements over FunctionRegion no longer compile. Add a default: case to fix:

// before
switch region {
case .usEast1: ...
// ❌ compiler error: switch must be exhaustive
}

// after
switch region {
case .usEast1: ...
default: ...
}

Test plan

• Existing FunctionsClientTests pass unchanged
• CI green across all platforms

[github-actions]

⚠️ Potential Breaking API Changes Detected

This PR appears to contain breaking API changes. Please review the changes below:

API Check Output

  💔 API breakage: enum FunctionRegion has been changed to a struct
  💔 API breakage: enumelement FunctionRegion.apNortheast1 is now static
  💔 API breakage: enumelement FunctionRegion.apNortheast1 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.apNortheast2 is now static
  💔 API breakage: enumelement FunctionRegion.apNortheast2 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.apSouth1 is now static
  💔 API breakage: enumelement FunctionRegion.apSouth1 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.apSoutheast1 is now static
  💔 API breakage: enumelement FunctionRegion.apSoutheast1 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.apSoutheast2 is now static
  💔 API breakage: enumelement FunctionRegion.apSoutheast2 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.caCentral1 is now static
  💔 API breakage: enumelement FunctionRegion.caCentral1 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.euCentral1 is now static
  💔 API breakage: enumelement FunctionRegion.euCentral1 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.euWest1 is now static
  💔 API breakage: enumelement FunctionRegion.euWest1 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.euWest2 is now static
  💔 API breakage: enumelement FunctionRegion.euWest2 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.euWest3 is now static
  💔 API breakage: enumelement FunctionRegion.euWest3 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.saEast1 is now static
  💔 API breakage: enumelement FunctionRegion.saEast1 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.usEast1 is now static
  💔 API breakage: enumelement FunctionRegion.usEast1 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.usWest1 is now static
  💔 API breakage: enumelement FunctionRegion.usWest1 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: enumelement FunctionRegion.usWest2 is now static
  💔 API breakage: enumelement FunctionRegion.usWest2 has declared type change from (Functions.FunctionRegion.Type) -> Functions.FunctionRegion to Functions.FunctionRegion
  💔 API breakage: constructor FunctionRegion.init(rawValue:) has return type change from Functions.FunctionRegion? to Functions.FunctionRegion

If this is intentional, please update your PR title or commit message to include:

• ! after the type (e.g., feat!: remove deprecated method)
• Or include BREAKING CHANGE: in the commit body

If this is a false positive, you can safely ignore this warning.

[coveralls]

Coverage Report for CI Build 28606932395

Coverage increased (+0.1%) to 81.215%

Details

• Coverage increased (+0.1%) from the base build.
• Patch coverage: 3 uncovered changes across 1 file (3 of 6 lines covered, 50.0%).
• 6 coverage regressions across 2 files.

Uncovered Changes

File	Changed	Covered	%
Sources/Functions/Types.swift	6	3	50.0%

Coverage Regressions

6 previously-covered lines in 2 files lost coverage.

File	Lines Losing Coverage	Coverage
Sources/Auth/Internal/Keychain.swift	5	37.23%
Sources/Auth/Storage/KeychainLocalStorage.swift	1	41.67%

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Coverage Stats

Relevant Lines:	9348
Covered Lines:	7592
Line Coverage:	81.22%
Coverage Strength:	36.8 hits per line

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💛 - Coveralls