feat: disable-reporting juju config option

[MichaelThamm]

Issue

Some users do not want to send anonymous usage statistics to stats.grafana.org. For example, in an air-gapped environment this may cause excess logs due to the endpoint being unreachable.

Solution

1. Adding a config option
   Add a juju config option to the loki charm. By default the config will send usage statistics and will not write to the config file. Only if the reporting-enabled option is set to false, then we write to the analytics block with reporting_enabled=false

2. Add and fix tests
   In an attempt to add scenario tests for testing this config option, the pin for ops=2.16 was removed and technical debt was removed to be compatible with the new ops.testing Scenario 7 syntax.

Context

Since we want to contribute to upstream open-source, we leave the default option as reporting enabled.

Testing Instructions

Note: Deploying --config reporting-enabled=true is functionally equivalent to not supplying a config.

1. Pack the charm
   charmcraft pack

Deploy Loki default

4. Deploy loki (reporting enabled by default)

juju deploy ./*.charm loki --resource loki-image=docker.io/ubuntu/loki:2-22.04 --resource node-exporter-image=docker.io/prom/node-exporter:v1.7.0 --trust
juju ssh --container loki loki/0 cat /etc/loki/loki-local-config.yaml | yq -r '.analytics'
-> null

5. Toggle the reporting config

juju config loki reporting-enabled=false
juju ssh --container loki loki/0 cat /etc/loki/loki-local-config.yaml | yq -r '.analytics'
-> reporting_enabled: false

6. Scale the application up

juju add-unit loki -n 1
jssh --container loki loki/1 cat /etc/loki/loki-local-config.yaml | yq -r '.analytics'
-> reporting_enabled: false

7. Toggle the config

juju config loki reporting-enabled=true
jssh --container loki loki/1 cat /etc/loki/loki-local-config.yaml | yq -r '.analytics'
-> null

Deploy Loki with reporting disabled

2. Deploy loki-off (reporting disabled)

juju deploy ./*.charm loki-off --resource loki-image=docker.io/ubuntu/loki:2-22.04 --resource node-exporter-image=docker.io/prom/node-exporter:v1.7.0 --config reporting-enabled=false --trust
juju ssh --container loki loki-off/0 cat /etc/loki/loki-local-config.yaml | yq -r '.analytics'
-> reporting_enabled: false

3. Toggle the reporting config

juju config loki-off reporting-enabled=true
juju ssh --container loki loki-off/0 cat /etc/loki/loki-local-config.yaml | yq -r '.analytics'
-> null

4. Scale the application up

juju add-unit loki-off -n 1
jssh --container loki loki-off/1 cat /etc/loki/loki-local-config.yaml | yq -r '.analytics'
-> null

5. Toggle the config

juju config loki-off reporting-enabled=false
jssh --container loki loki-off/1 cat /etc/loki/loki-local-config.yaml | yq -r '.analytics'
-> reporting_enabled: false

Upgrade Notes

[sed-i]

Nice!