In-memory provider for e2e testing and minimal SDK usage

[Kavindu-Dodan]

As proposed by OFEP: SDK end-to-end test strategy ¹, we should create an in-memory provider for Java-sdk

We already have contributions for Python² & Go ³, and we can use same flag format, constructors & error handling strategy for this implementation.

• Implement the in-memory provider
• Migrate existing e2e tests⁴ to newly create in-memory provider
  • search repo for https://github.com/open-feature/java-sdk/issues/523 for related TODOs.

Footnotes

1. https://github.com/open-feature/ofep/pull/71 ↩

2. https://github.com/open-feature/python-sdk/pull/157 ↩

3. https://github.com/open-feature/go-sdk/pull/192 ↩

4. https://github.com/open-feature/java-sdk/tree/main/src/test/java/dev/openfeature/sdk/e2e ↩

[toddbaert]

Small related PR here: #543

[liran2000]

@Kavindu-Dodan @toddbaert as PR merged, can be resolved ?

[Kavindu-Dodan]

@liran2000 yes, this is complete. Thank you for working on this 🙌