Pick right PHP version for sites created before introducing the PHP selector

[fluiddot]

Related to #240 (comment) and #225.

Proposed Changes

• Populate the PHP version for sites without this property specified when loading site details from user data. The PHP version used for those sites is 8.0, as it was the default version used before Bump default PHP version to 8.1 #240 got merged.

Testing Instructions

New sites

1. Create a new site.
2. Go to the Settings tab.
3. Observe that the PHP version is 8.1.
4. Open WP admin and navigate to wp-admin/site-health.php?tab=debug.
5. Open the Server section.
6. Observe that the PHP version is 8.1.

Old sites

1. Install a version of the Studio app before changes from Allow PHP version to be changed from Site Settings #225 were applied.
   • Alternatively, you can edit the file ~/Library/Application\ Support/Studio/appdata-v1.json and remove phpVersion property from sites.
2. Create a new site.
3. Build/install a version with the changes from this PR.
4. Select the previously created site.
5. Go to the Settings tab.
6. Observe that its PHP version is 8.0.
7. Edit the PHP version.
8. Observe that in the "Edit PHP version" modal, the version 8.0 is selected.

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[wojtekn]

The code change looks clear and the feature works as expected.

[dcalhoun]

@fluiddot alright, I'm going to "bite." 😄 What is this doing and why is it necessary? 😆

Joking aside, I'd love to understand this logic. It's a bit cryptic to me. Would you be willing to share any insight you have? Thanks! 🙇🏻

[fluiddot]

@dcalhoun I'm glad you asked about this 😃 .

This type is basically an extension of Partial's TypeScript utility type to make all nested properties optional. Partial only sets as optional the root ones. As an example, here's the UserData type:

export interface UserData {
	sites: SiteDetails[];
	snapshots: Snapshot[];
	devToolsOpen?: boolean;
	authToken?: StoredToken;
	onboardingCompleted?: boolean;
	lastBumpStats?: {
		[ group: string ]: {
			[ stat: string ]: number;
		};
	};
	promptWindowsSpeedUpResult?: PromptWindowsSpeedUpResult;
}

If you make Partial<UserData>, all the above properties will be optional:

{
    sites?: SiteDetails[] | undefined;
    snapshots?: Snapshot[] | undefined;
    devToolsOpen?: boolean | undefined;
    authToken?: StoredToken | undefined;
    onboardingCompleted?: boolean | undefined;
    lastBumpStats?: {
        ...;
    } | undefined;
    promptWindowsSpeedUpResult?: PromptWindowsSpeedUpResult | undefined;
}

However, for instance, the nested properties of SiteDetails like SiteDetails.id won't be optional. I found this situation while writing this unit test, and needed to mock the persisted user data. In my case, I only wanted to define part of the site details. That's why I introduced this extra utility type. I presume that we might need it in the future in similar cases, mostly when adding unit tests.