[JAVA-02] Add OAuth, tenant context, errors, retries, and Spring integration guidance #3

@jaavid

Background

CoreLink is one product across multiple implementation repositories. This work is owned by sdk-java under EPIC-05.

Goal

Add OAuth, explicit tenant context, typed errors/retries and Spring integration guidance against version-identifiable contracts, with retained Beta conformance evidence.

Parent

• Primary Product Epic: EPIC-05
• Backlog ID: JAVA-02

Scope

• Implement authentication and tenant context on the JAVA-01 generated baseline.
• Add typed error/retry behavior and Spring-oriented integration guidance.
• Preserve generated contract provenance and avoid hand-written schema drift.
• Validate supported behavior against MOCK-02/MOCK-03 or equivalent accepted sandbox.

Out of Scope

• Stable artifact publication; that remains JAVA-03.
• Advertising draft/scaffold contract slices as supported.
• Product-runtime acceptance outside the SDK boundary.

Acceptance Criteria

• OAuth/authentication and tenant context are explicit and least-privilege.
• Error/retry semantics map to exact accepted contract behavior.
• Spring guidance is runnable and identifies SDK/contract maturity.
• Cross-tenant and insufficient-scope paths fail closed.
• Positive, denied, malformed, retry and recovery paths are repeatable against an accepted mock/sandbox.
• Generated provenance is preserved and retained evidence advances EPIC-05.

Dependencies and acceptance state

• Execution prerequisite: JAVA-01 reproducible generation/provenance baseline.
• Contract inputs: accepted/version-identifiable API-02/API-03/API-04 slices as required by the supported Java surface; draft implementation may proceed only with explicit maturity.
• Conformance input: MOCK-02 / MOCK-03 or equivalent accepted sandbox before Beta support claims.
• Blocks: JAVA-03 signed artifact/release work, DOCS-04 Java guidance, WEB-03 supported-tool claims, and EPIC-05 Java SDK acceptance.
• Current dependency state: See the CoreLink Product organization Project.

Planning Metadata

• Type: Feature
• Priority snapshot: P1
• Product milestone snapshot: Beta
• Domain snapshots: sdk, devex
• Area snapshot: package
• Complexity: L
• Created in status: Triage
• Current status and DRI: See the CoreLink Product organization Project.
• Intended repository labels: type:feature

Definition of Done

• Acceptance criteria demonstrated.
• Required conformance evidence passes on version-identifiable dependencies.
• Contract compatibility and generated provenance are reconciled.
• Security and tenant boundaries are reviewed.
• Documentation and Spring examples are runnable.
• Pull request(s), dependency versions and retained evidence are linked.