[Frontend] Clear reports and datapoints state when switching agencies

[terryttsai]

Description of the change

https://www.loom.com/share/8ec11e17e8004218859c43a77141a461

Set up reactions to clear reports and datapoints state when user switches agencies.

For the Reports page, we only fetch the reports list when the user navigates to that page, OR the user agency id has changed.

For the Metrics page, we only fetch the datapoints when the user navigates to that page, OR the user agency id has changed.

This means if the user switches agencies while on a different page, we clear, but don't fetch the new data until the user visits a page that needs to load that data, minimizing needless fetches.

Type of change

All pull requests must have at least one of the following labels applied (otherwise the PR will fail):

Label	Description
Type: Bug	non-breaking change that fixes an issue
Type: Feature	non-breaking change that adds functionality
Type: Breaking Change	fix or feature that would cause existing functionality to not work as expected
Type: Non-breaking refactor	change addresses some tech debt item or prepares for a later change, but does not change functionality
Type: Configuration Change	adjusts configuration to achieve some end related to functionality, development, performance, or security
Type: Dependency Upgrade	upgrades a project dependency - these changes are not included in release notes

Related issues

Closes #15

Checklists

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[terryttsai]

Following the advice here https://stackoverflow.com/questions/59345330/how-do-you-dispose-a-reaction-defined-in-a-class-constructor to handle disposing of a reaction defined in a mobx class, this might be overkill since at least right now we never need to dispose of this since we never need to de-instantiate any of our mobx stores

[lilidworkin]

@terryttsai this is very cool!

I tried it out locally and one thing I noticed is that if you switch to a different agency while on a particular report, you get an error:

This is probably fine (I'm not sure what the right behavior should be in this case?) but just wanted to call it out in case there's an easy fix.

[terryttsai]

Thanks for calling that out, I put up a fix for this case by navigating you back to the reports list when you try to switch agencies while on a report: https://www.loom.com/share/f99f609f88e44633868835bc80363ef9

I also replace the browser navigation stack so you can't press the back button and go back to that report page since you'd see an error there.

[lilidworkin]

yay!