Add README on hack/ folder resources

Contains a few short explanatory sentences and instructions on the
various deployments and when/how to use them, including cleanup for the
S3 volume.

Also contains a mock credential file for running zero-config integration
tests on blockstore puts (with `LakeFSFileSystem.put_file_to_blockstore`)
in the case of S3 via SeaweedFS.

hack/README.md

@@ -0,0 +1,64 @@
+# Useful resources for development on `lakefs-spec`
+
+This document contains information on the resources in this directory, and how they can be used in development and testing.
+
+## `docker-compose.yml` - local lakeFS quickstart instance
+
+This Docker Compose file bootstraps a local [lakeFS quickstart instance](https://docs.lakefs.io/quickstart/launch.html).
+It does not come with an associated volume, so you can spin it up and down without creating dangling resources.
+
+Requirements:
+* A Docker runtime & CLI with `docker compose`.
+
+To bootstrap, run the following command:
+
+```shell
+docker compose -f hack/docker-compose.yml up
+```
+
+To stop the container again, run
+
+```shell
+docker compose -f hack/docker-compose.yml down
+```
+
+## `lakefs-s3-local.yml` - lakeFS with a local, SeaweedFS-backed S3 blockstore
+
+For simulating a lakeFS deployment with a remote blockstore, the `lakefs-s3-local.yml` Docker Compose file contains a
+recipe mocking an S3 blockstore using SeaweedFS.
+
+To bootstrap this setup, run the command
+
+```shell
+docker compose -f hack/lakefs-s3-local.yml up
+```
+
+To stop the containers again, run
+
+```shell
+docker compose -f hack/lakefs-s3-local.yml down
+```
+
+To clean the created volume, e.g. for when you want to remove created storage namespaces after repository deletions,
+you can nuke the deployment like so:
+
+```shell
+docker compose -f hack/lakefs-s3-local.yml rm
+docker volume rm hack_seaweedfs-data
+```
+
+## Mock credentials for direct blockstore writes with the `LakeFSFileSystem`
+
+In order to write to the local S3 blockstore using `LakeFSFileSystem.put_file_to_blockstore`, you can use the following
+mock credentials:
+
+```shell
+cat > $HOME/.aws/credentials <<EOL
+[default]
+endpoint_url = http://localhost:9001
+aws_access_key_id = sandbox
+aws_secret_access_key = sandbox
+EOL
+```
+
+Beware that this will overwrite any existing credential files, so it is recommended to back those up first.