Custom the save method of the Rule model to handle the annotation "rule"

[hoangpn]

When creating or updating a rule on Promgen, the corresponding rule data on Prometheus will be given an annotation "rule" that is the link to that rule on Promgen. However, the annotation rule on Promgen always has the URI "/rule/0" because it has not been intentionally set up:

• Previously, the value of annotation["rule"] on Promgen was accidentally set when loading data from the AlertRuleForm. Specifically, in the form's clean() method, there is a declaration of prometheus.check_rule(), which includes a serializer that automatically adds the annotation["rule"]. Since Python is pass-by-object-reference, annotation["rule"] of the rule will be automatically set whenever we create or update it.
• After the commit 2761419, to handle the case of calling prometheus.check_rule() when creating a new rule, a temporary line of code setting rule.pk=0 was added. Since this is a shared form between creating and updating, the value of annotation["rule"] for both cases becomes /rule/0.
• The actual value of annotation["rule"] on Prometheus is not affected because it will be serialized again before each time it is sent to Prometheus. https://github.com/line/promgen/blob/master/promgen/signals.py#L173

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To ensure data is synced between Promgen and Prometheus, I customize the save method of the Rule model.
This solution will help keep the data in the database synchronized and requires minimal changes while still affecting all processes such as displaying, creating, updating, cloning, or importing rules.

Before:
Data displayed on Rule page after creating or updating rule:

After:
Data displayed on Rule page after creating or updating rule:

[vincent-olivert-riera]

I have reviewed and tested your code. It works fine :)

However, I have some minor suggestions I would like you to fix.

Apart from the suggestions I have made here in GitHub, could you please wrap the lines in your commit message at 100 characters?

Thank you very much!

[hoangpn]

@vincent-olivert-riera
Thank you for your comments. I have updated the source code according to your suggestion by a fix-up commit.

[vincent-olivert-riera]

@vincent-olivert-riera Thank you for your comments. I have updated the source code according to your suggestion by a fix-up commit.

Looks good to me 👍

Please squash the fixup commits for final review. Don't forget to change the commit message to wrap all lines at 100 characters.

[hoangpn]

Thank you for your hard work. I squashed the fix-up commits and reformatted the commit message too. 👍