docs(contributing): require DCO sign-off on every commit

Same DCO block landing in axonflow-sdk-rust#1, applied uniformly across
all org repos so the org-wide DCO GitHub App check is documented in
each repo's CONTRIBUTING.md.

Signed-off-by: Saurabh Jain <saurabhjain1592@gmail.com>

Author: saurabhjain1592

CONTRIBUTING.md

@@ -1,34 +0,0 @@
-# Contributing to AxonFlow Java SDK
-
-Thank you for your interest in contributing! Please open an issue or pull request via the [GitHub repository](https://github.com/getaxonflow/axonflow-sdk-java).
-
-## Development setup
-
-```bash
-./mvnw verify
-```
-
-Tests run under JUnit 5. The wire-shape contract gate (under `scripts/wire_shape/`) runs in CI when a PR touches Java sources, the wire-shape baseline, or the gate scripts themselves — see `.github/workflows/wire-shape-contract.yml` for the exact path filter.
-
-## Pull request guidelines
-
-1. Keep PRs focused — one feature or fix per PR.
-2. Update `CHANGELOG.md` under `[Unreleased]` for user-visible changes.
-3. Ensure `./mvnw verify` is green and the wire-shape contract gate passes.
-4. Prefer Jackson `@JsonProperty` on a `@JsonCreator` constructor for any new wire-bound POJO field — that propagates serialization both ways without hand-rolled transformer code.
-
-## Baseline burndown policy
-
-The wire-shape contract gate uses a baseline file (`tests/fixtures/wire-shape-baseline.json`) to grandfather pre-existing drift findings — the gate fails on any *new* drift but tolerates the listed entries. The baseline exists to land the gate without a giant cleanup PR; it is not intended to be permanent.
-
-When your PR touches a type listed in the baseline, do one of:
-
-- **Burn it down.** Realign the POJO with the OpenAPI spec in this PR, regenerate the baseline via `scripts/wire_shape/refresh.py`, and note "burndown: `<entry>`" in the PR description.
-- **Justify it.** If the drift can't be resolved in this PR (different scope, blocked on a platform spec change, etc.), say so in the PR description in one line.
-
-CI does not block PRs that touch a baselined type without addressing it, but reviewers will ask the burndown-or-justify question.
-
-## Questions
-
-- Open a GitHub issue
-- Email: hello@getaxonflow.com