Contextual identity information in cookies API

[rebloor]

Documentation of the cookies API does not include information about contextual identities. For example, cookies.CookieStore only talks about there being different stores for private vs. non-private windows.

(Consider combining with Bug 1750589 More documentation for developers about cookieStoreId field of proxy.RequestDetails.)

[Rob--W]

The cookieStoreId concept originated from Chrome, where it was used to distinguish between incognito and non-incognito mode (aka private browsing and non-private browsing mode in Firefox).

When the contextual identities feature (possibly more well-known as "container tabs") was introduced, this concept was expanded to also include containers.

Later on, this cookieStoreId property was added to other extension APIs where the distinction between container tabs was relevant.

The article at https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Work_with_contextual_identities can be improved, to serve as the canonical location for cookieStoreId documentation (and be referenced by all MDN articles that mention cookieStoreId).

• "APIs for working with contextual identities" can have another enumeration of all APIs that support cookieStoreId
• "Permissions" can be expanded to explain that the use of cookieStoreId requires the "cookies" permission if that API allows the modification of cookies. For example, in the tabs.query API, cookieStoreId does not require the "cookies" API since reading the property doesn't affect the integrity of cookies in containers. Using tabs.create on the other hand does, because it allows the creation of cookies in a specific container. This relaxed permission requirement was introduced in https://bugzilla.mozilla.org/show_bug.cgi?id=1662329 (see bug for more context).

[rebloor]

Thanks @Rob--W

[hamishwillee]

Thanks. @rebloor I assume you're assigning yourself to this task?

[rebloor]

If, or hopefully when, get to it, I will @hamishwillee

[Rob--W]

Update the links in the downloads documentation when there is a canonical place for cookieStoreId documentation, see https://github.com/mdn/content/pull/8106#pullrequestreview-744412976

[Rob--W]

There is an introduction to containers at https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/contextualIdentities, but it does not mention cookieStoreId or https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Work_with_contextual_identities . Could you fix that too?