feat: adding mobile/desktop pagespeed strategy

[akashmannil]

Adding Pagespeed desktop/mobile strategy.

Fixes #3453

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[dmythro]

Thanks for jumping on this so fast!

Couple things Claude spotted and I want to mention, might make sense:

1. Strategy is immutable after creation — disabled={isEditMode} on the Select. If you want to switch a
   monitor from desktop to mobile, you must delete and recreate it. The server-side editMonitorBodyValidation
   does allow strategy though, so the API permits changes but the UI blocks it. This inconsistency could cause
   confusion.
2. strategy column added to ALL monitors, not just pagespeed. Every http, ping, docker, etc. monitor gets
   strategy = 'desktop'.

I think editing should be allowed - so I can just switch existing monitors to mobile without re-adding new ones and without paused old monitors for historical data. And strategy should be empty by default, only set for pagespeed.

[akashmannil]

Thanks for the review @dmythro. PFB thought process for each of the mentioned pointers.

1. Once we change the strategy, our history gets invalidated (our previous data points to Desktop, but later changed to mobile gives different stats - faulty assurances). Thats why we're making it immutable.
2. Since http pagespeed monitor is the only option with reliable pagespeed accessibility metrics (which is expected to be varying based on device pref) with proper strategy dependencies, we're adding only an option for that.

[ajhollid]

Some minor issues to resolve, but it generally looks good.

Allowing editing of the strategy type is a design decision; we can defer to @gorkem-bwl on that one.

My personal opinion is to agree with you that it should be immutable once set, as the historical data will be nonsensical if you switch strategies.

The precedent has been set for allowing these types of history-breaking changes, though, so I'll leave this one to @gorkem-bwl to make the call.

[gorkem-bwl]

Some minor issues to resolve, but it generally looks good.

Allowing editing of the strategy type is a design decision; we can defer to @gorkem-bwl on that one.

My personal opinion is to agree with you that it should be immutable once set, as the historical data will be nonsensical if you switch strategies.

The precedent has been set for allowing these types of history-breaking changes, though, so I'll leave this one to @gorkem-bwl to make the call.

My take here is that user knows what he's doing, so we could agreeable for the user to edit that section.

[dmythro]

As a user I'd prefer to edit this. At least I hope you won't block editing strategy via API.

I have many monitors and creating new for each and pause old ones is much more hassle than just switch to mobile and know that older data was desktop is fine with me.

[ajhollid]

Looks pretty good. There's an error in the montor validation that will set strategy to non-pagespeed type monitors that needs to be fixed, I think we're done after that.

[akashmannil]

@ajhollid Default values removed and set only for pagespeed monitors. Please do let me know if this looks ok. Thanks!