Implement Polaris

[samlamont]

Polaris is an implementation of an Iceberg REST catalog that provides "centralized, secure read and write access to your Iceberg tables across different REST-compatible query engines." Ref: https://polaris.apache.org/releases/1.5.0/

Some notes as I understand them currently:

• It supports fine-grained control of access to realms, catalogs, namespaces, and tables through credential vending.

• Roles and privileges are defined in polaris as principal roles (ie., "iceberg-catalog-admin" or "iceberg-namespace-restricted-read" which can define table-level privileges). These can be mapped to users via keycloak then registered with polaris so that polaris can understand what privileges correspond to each token it receives.

• Spark and Trino can be configured to access the polaris catalog(s) (we need to updated create_spark_session() and const.py in teehr)

• Jupyterhub can be configured to parse the privileges from the user's keycloak token using the JUPYTERHUB_CRYPT_KEY

This is being developed in this branch: https://github.com/RTIInternational/teehr-hub/tree/implement-polaris

[samlamont]

I think this needs to be added to teehr/const.py

# Polaris / OAuth2
POLARIS_USER_TOKEN = os.environ.get("POLARIS_USER_TOKEN", "")
POLARIS_OAUTH2_SERVER_URI = os.environ.get("POLARIS_OAUTH2_SERVER_URI", "")
SPARK_POLARIS_CLIENT_SECRET = os.environ.get("SPARK_POLARIS_CLIENT_SECRET", "")
POLARIS_DEFAULT_REALM = os.environ.get("POLARIS_DEFAULT_REALM", "teehr")