Automate downstream unit testing. See
databrickslabs/sandbox#141 for more details.

Fix 'Builder' object has no attribute 'sdk_config' error.

* Check UCX and LSQL for backwards compatibility
([#78](#78)). In this
release, we introduce a new GitHub Actions workflow, downstreams.yml,
which automates unit testing for downstream projects upon changes made
to the upstream project. The workflow runs on pull requests, merge
groups, and pushes to the main branch and sets permissions for id-token,
contents, and pull-requests. It includes a compatibility job that runs
on Ubuntu, checks out the code, sets up Python, installs the toolchain,
and accepts downstream projects using the
databrickslabs/sandbox/downstreams action. The job matrix includes two
downstream projects, ucx and remorph, and uses the build cache to speed
up the pip install step. This feature ensures that changes to the
upstream project do not break compatibility with downstream projects,
maintaining a stable and reliable library for software engineers.
* Fixed `Builder` object has no attribute `sdk_config` error
([#86](#86)). In this
release, we've resolved a `Builder` object has no attribute `sdk_config`
error that occurred when initializing a Spark session using the
`DatabricksSession.builder` method. The issue was caused by using dot
notation to access the `sdk_config` attribute, which is incorrect. This
has been updated to the correct syntax of `sdkConfig`. This change
enables successful creation of the Spark session, preventing the error
from recurring. The `DatabricksSession` class and its methods, such as
`getOrCreate`, continue to be used for interacting with Databricks
clusters and workspaces, while the `WorkspaceClient` class manages
Databricks resources within a workspace.

Dependency updates:

* Bump codecov/codecov-action from 1 to 4
([#84](#84)).
* Bump actions/setup-python from 4 to 5
([#83](#83)).
* Bump actions/checkout from 2.5.0 to 4.1.2
([#81](#81)).
* Bump softprops/action-gh-release from 1 to 2
([#80](#80)).

Added catalog and schema parameters to the fetch and execute command.
Created unit and integration tests.

* Added catalog and schema parameters to execute and fetch
([#90](#90)). In this
release, we have added optional `catalog` and `schema` parameters to the
`execute` and `fetch` methods in the `SqlBackend` abstract base class,
allowing for more flexibility when executing SQL statements in specific
catalogs and schemas. These updates include new method signatures and
their respective implementations in the `SparkSqlBackend` and
`DatabricksSqlBackend` classes. The new parameters control the catalog
and schema used by the `SparkSession` instance in the `SparkSqlBackend`
class and the `SqlClient` instance in the `DatabricksSqlBackend` class.
This enhancement enables better functionality in multi-catalog and
multi-schema environments. Additionally, this change comes with unit
tests and integration tests to ensure proper functionality. The new
parameters can be used when calling the `execute` and `fetch` methods.
For example, with a `SparkSqlBackend` instance `spark_backend`, you can
execute a SQL statement in a specific catalog and schema with the
following code: `spark_backend.execute("SELECT * FROM my_table",
catalog="my_catalog", schema="my_schema")`. Similarly, the `fetch`
method can also be used with the new parameters.

* Fixing ovewrite integration tests
([#92](#92)). A new
enhancement has been implemented for the `overwrite` feature's
integration tests, addressing a concern with write operations. Two new
variables, `catalog` and "schema", have been incorporated using the
`env_or_skip` function. These variables are utilized in the `save_table`
method, which is now invoked twice with the same table, once with the
`append` and once with the `overwrite` option. The data in the table is
retrieved and checked for accuracy after each call, employing the
updated `Row` class with revised field names `first` and "second",
formerly `name` and "id". This modification ensures the proper operation
of the `overwrite` feature during integration tests and resolves any
related issues. The commit message `Fixing overwrite integration tests`
signifies this change.