CCM-22997: Shared utilities

[rhyscoxnhs]

Description

Introduces a new publishable package, @nhsdigital/nhs-notify-shared-utils, in a new
packages/ workspace. It holds generic, technical-only utilities for reuse across NHS
Notify bounded contexts.

Each module is a subpath export, so a consumer imports only what it needs and Lambda
bundles never pull in unused code:

• ./logger — a generic pino-backed Logger. Redaction is fully opt-in: the class
  declares no redact paths of its own; each bounded context supplies its own via
  redactPaths.
• ./lambda-utils — parseEnv / EnvValidationError, a pure formatZodIssues
  formatter, and SQS string-attribute readers. parseEnv validates process.env (or a
  supplied source) against a Zod object schema, so callers get coercion (numbers,
  booleans, etc.) and format assertions rather than every variable being read as an
  untyped string; issues are thrown as a single formatted EnvValidationError. Neither
  helper takes a hard dependency on Zod — EnvSchema<T> and FormattableZodIssue
  declare the minimal structural shape needed, so any Zod schema/error is accepted
  without coupling the package to a Zod version. No AWS SDK dependency.
• ./s3-json — a get-JSON-from-S3-and-optionally-validate helper.

Integration test-support helpers (AWS client factories, polling primitives, event-factory
fixtures) were deliberately not included — they're boilerplate enough to copy into
each repo's tests rather than maintain as a shared dependency, per review feedback.

Dependency and build contract:

• pino and @aws-sdk/client-s3 are peer dependencies (the S3 client optional),
  preventing duplicate copies in consumer bundles.
• CommonJS build via tsc with a split tooling/build tsconfig; files restricted to
  dist. Every module ships a README with usage.

Workspace and release wiring:

• Adds the packages/* workspace glob, aws and runtime pnpm catalogs, a
  cache-correct turbo build task, and ESLint coverage for the new package.
• Adds a tag-driven publish workflow (publish-packages.yaml) to GitHub Packages under
  @nhsdigital, triggered only by shared-utils-v* tags and decoupled from the
  Terraform module release. It fails unless the pushed tag version matches package.json
version. Least-privilege permissions (contents: read, packages: write),
  GITHUB_TOKEN auth only.
• Adds a tag-shared-utils-release.yaml workflow that automatically creates and pushes
  the shared-utils-vX.Y.Z tag once the main CI/CD pipeline completes successfully on
  main, reading the version straight from package.json. This removes the manual,
  error-prone step of a developer creating a tag that must match the package version by
  hand — bumping version in a merged PR is now the only manual step required to
  release.
• Updates existing tsconfigs to resolve typecheck / unit test failures due to missing
  jest entry in types and use of deprecated baseUrl properties.
• 100% unit-test coverage; lint, typecheck, tests and build are green.

Context

The app-response and client-callbacks bounded contexts independently built
near-identical technical utilities — structured logging, environment-variable
validation, and error formatting. Maintaining two copies causes drift and doubled
effort. This extracts the generic, technical-only utilities into a single versioned
package so bounded contexts can depend on one shared implementation, keeping the
dependency one-way (bounded context → shared) and leaving all domain logic in its own
context. Integration test-support helpers were intentionally left out of the shared
package — they're low-risk boilerplate best copied per repo rather than centrally
maintained. Consumers adopt the package on their own cadence in follow-up work; this
change only introduces the package in the host repository.

Ref: CCM-22997.

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• I am familiar with the contributing guidelines
• I have followed the code style of the project
• I have added tests to cover my changes
• I have updated the documentation accordingly
• This PR is a result of pair or mob programming

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• I confirm that neither PII/PID nor sensitive data are included in this PR and the codebase changes.