T2R should respect Locale of Red'User or_else Red'Server or_else BrowserClient

[tonischilling]

Bug summary
When using T2R from Germany and picking a date in the DatePicker (or just use the current date),
it will be transformed to the _date of the previous day,
giving a wrong search interval for the Redmine-TimeEntries.

To Reproduce

1. choose Timezone Germany in your Redmine-Account
2. produce some Activities on some consecutive days (e.g October 4,3,2,1),
   Steps to reproduce the behavior:
3. Go to '...'
4. Click on '....'
5. Scroll down to '....'
6. See error

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add screenshots to help explain your problem.

Device information

• Type: [e.g. Desktop / Laptop / Handheld]
• OS: [e.g. Windows 10 / Ubuntu 18.4 / MacOS 10.14.4]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.

[tonischilling]

Hrrrg! Sorry, somehow I hit [save], before I finished the description.

[tonischilling]

Description continued ...

Steps to reproduce
3. add comments to these activities (2./3./4.Okt),
telling the date (:spent_on) of the activity: e.g. "am 2/3/4.Oktober"
4. choose 4.Okt.2021 in T2R-DatePicker
Table "Time-Logged-In-Redmine" will show "am 3.Oktober"

Expected result:
Table "Time-Logged-In-Redmine" should show "am 4.Oktober"

[tonischilling]

I hacked this into t2r.js to find the reason:

[tonischilling]

I got this in the Developer-Console:

Internally the time part of the ISO-string will be cut off and replaced by "00:00:00Z",
giving us the previous day when fetching the Redmine entries.

[tonischilling]

my suggestion:
Instead of dealing with the User-Locale on browser-side,
it would be better, to send the picked date "as is" to the Rails-Action.
On Rails-side the users | redmines |servers locale is well known, ...

[tonischilling]

Context:

• using Toggl2Redmine-4.3.1, Redmine-4.2.2, Rails-5.2.6, Ruby-2.7.4
• I used different browsers