Don't error if user has disabled all site storage in their browser

[baltpeter]

We received an error report where most of our pages were unusable due
to a "No available storage method found" error from localForage. As the
message implies, this error occurs if the user has disabled all site
storage in their browser and localForage can't find any backend to
write to.

I was able to reproduce this both in Chrome and Firefox. In Chrome, you
can disable all site storage by going to chrome://settings/cookies and
choosing "Block all cookies (not recommended)". In Firefox, it's more
hidden and per-site. Open the site and press Ctrl + I to open the "Page
Info" dialog. Click "Permissions" and disable "Set cookies".

Obviously, disabling site storage shouldn't make our site fail. After
all, we even explicitly allow users to turn that off on our site! Thus,
the solution is quite simple: Instead of defaulting to "true" for the
corresponding privacy controls, we should default according to whether
the user has enabled site storage.

Since all browsers seem to tie disabling localStorage et al. to
disabling cookies, we can just check whether cookies are enabled for
this feature detection and there's the very handy
navigator.cookieEnabled property for that.

[cypress]

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Test summary

67 • 0 • 8 • 0 • 0

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Run details

Project	datenanfragen/website
Status	Passed
Commit	6ebee8c
Started	Aug 16, 2022 5:28 PM
Ended	Aug 16, 2022 5:31 PM
Duration	03:08 💡
OS	Linux Debian - 10.9
Browser	Electron 91

View run in Cypress Dashboard ➡️

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[mal-tee]

LGTM, thank you!

[mal-tee]

Do we have a regression here? We just got this error report:

message := Uncaught UnknownError: The user denied permission to access the database.
type := error
colno := 18078
filename := https://www.datarequests.org/js/commons.bundle.gen.js
lineno := 19
error.code := 0
error.message := The user denied permission to access the database.
error.description := Unexpected error while opening IndexedDB in PrivacyAsyncStorage.getDb
[error.name](http://error.name/) := UnknownError
error.enduser_message := An unexpected error occured while trying to access the database in your browser.
error.context.options.storeName := proceedings
[error.context.options.name](http://error.context.options.name/) := Datenanfragen.de

[baltpeter]

@mal-tee The problem was probably that this PR only sets the default but not the dnt default. So if the user had enabled DNT and disabled cookies, this error can occur.

This will be fixed in #1166, though I guess that doesn't matter too much anymore since Firefox has since removed DNT support…