Update pip packages' versions with `tox -e update-requirements`.

Modify .gitignore in order to ignore any .VSCode directory.

Introduce CONTRIBUTING.md file with essential instructions for
contributing to the charm's code.

Generate upstream Tensorboards Web App manifests and keep the relevant
parts as Jinja2 templates.

Update pip packages' versions with `tox -e update-requirements`.

Add _log_and_set_status(), which is a copy from the function of the same
name in istio-pilot charm.

Modify configure_mesh() function to set status to `blocked` when there
is no ingress relation available. We decided upon this behaviour since
as a web app charm, it will be useless if it cannot be accessed.

- Rewrite charm following the sidecar pattern and using Pebble to manage
  the workload. Jupyter-UI charm was used as an example for this rewrite.
- Modify metadata.yaml to:
   - add a container
   - include information like website, source, docs, description
   - modify oci-image name
- Import KubernetesServicePatch library using `charmcraft fetch-lib`.

- Pin juju in requirements-integration file to ensure compatibility with
  controller version 2.9.
- Modify image-path and resources to reflect changes in the
  metadata.yaml of TWA charm.
- Deploy TWA with trust=True argument.
- Update test to relate TWA and istio-pilot charms with ingress relation
  in order to avoid TWA charm from getting in `blocked` status.

- Update requirements-unit files
- Modify tox.ini unit tests command
- Write tests to check that:
  - charm waits if it's not the leader
  - charm is blocked when there is no ingress relation.
  - charm is active when there is an ingress relation
  - Pebble layer is created with expected values
  - K8S resource handler is executed as expected

 - Introduce integration environment in tox.ini file
 - Create requirements-integration files
 - Write tests to check that:
    - charm is built and deployed with expected status
    - unit's status changes when charm is related with istio-pilot:ingress
    - TWA's UI is accessible through its address:port

- Istio-pilot's gateway relation was renamed to gateway-info. See
canonical/istio-operators#112
- Both Tensorboards charms are rewritten following the sidecar pattern
and need to be `juju` deployed with `--trust` argument.

Bump SDI version by removing pin in all requirements files

- Use K8sResourceHandler with labels and resource types arguments
- Modify pebble check name
- Fetch container name from metadata.yaml

Stop exposing the Tensorboards Web App's 'containerPort' as configurable
through the charm's config. This is neither an option likely to be
required by the end-user, nor actually supported by the WA itself.

When deploying Kubeflow, all web apps should use `production` mode to
ensure proper user authentication. Otherwise, every user is being
treated as admin. See kubeflow/kubeflow#5566

Add headers to the request sent during integration tests in order to be
able to fetch the TWA's UI.

- Modify on_remove to use krh.delete() function
- Rename err to error in all instances
- Remove container connection check since it is done by update_layer()
- Set status in _on_event instead of _configure_mesh()
- Stop logging inside check_leader

Modify charm message when there is no ingress relation available.