grafana-dashboard requests not properly deserialized

[Alvaro Uria]

A year ago, the grafana-dashboard interface was implemented, allowing related applications to share dashboards via the charms.reactive Request/Response pattern [1].

When I tested with prometheus-libvirt-exporter "register_dashboard" requests, I got:
"""
Error importing dashboard "libvirt": [{"classification":"DeserializationError","message":"json: cannot unmarshal string into Go value of type models.SaveDashboardCommand"},{"fieldNames":["Dashboard"],"classification":"RequiredError","message":"Required"}]'
"""

dashboards.new_requests list should have the dash.dashboard attribute checked [2]. If isinstance(dash.dashboard, str), then use json.loads(dash.dashboard):
"""
for dash in dashboards.new_requests:
    dash_obj = dash.dashboard
    if isinstance(dash_obj, str):
        dash_obj = json.loads(dash_obj)
    success, reason = import_dashboard(dash_obj, dash.name)
"""
Note: import_dashboard should return: (True, None)

1. https://charmsreactive.readthedocs.io/en/latest/patterns.html
2. see import_dashboards function on reactive/grafana.py

[Ryan Farrell (whereisrysmind)]

It think we could fix this by further improving the import_dashboard function to handle multiple data types. Check if 'dashboard' is a string, then attempt to convert it into a dictionary with json.loads; if that fails then it can return the its 'success' status and the reason being "cannot convert strng to json"

Logging needs to be implemented in the reactive code for import_dashboards to report the import status and reason, in any case.