Adding Accept-Language-header to interceptor

[Angamanga]

This pull request makes the following changes:
-Adding Accept-Language header to send the user-selected language to Auth-interceptor

Testing checklist:

• Switch language to Spanish (Spanish is the only translations we have right now)

• Try signing up with an email address already known

• The Error-message should be in Spanish

• GO to settings-categories

• Add a category with the same name as one that already exists

• The error message (or part of it, its not all translated yet) should be in Spanish

• Any other error-messages showing up as the error-toast-bar should be translated (it there are corresponding translations in the backend)

• I certify that I ran my checklist

Fixes ushahidi/platform# .

Ping @ushahidi/platform

[rowasc]

Lets get this into the release since David will need it, and make sure Walter tests it? @Angamanga
this should be the only extra change going into it except for the bugfix you are doing for filters , sorry 😬 !

[Angamanga]

@rowasc Yep, plus the backend-changes, right?

[rowasc]

yep sending both

[Angamanga]

@Obadha2 This will be included in the release too, could you test in Steve Buscemi? 🎉 🙏

[tuxpiper]

just a heads up : I've had trouble testing this with firefox on my localhost , the header was not changed after switching languages.

will give it another try tomorrow with other browsers / steve-buscemi

[tuxpiper]

mmm ok nevermind about my previous comment. I must have been too tired.

[theobadha]

@Angamanga while running smoke tests, i noticed the following:
From an old account, when I change language from General settings, language changes don't come into effect when I click Save, I have to log out of the account. When logged out, then the new language changes are seen.
However, I created a new account. When I change language from General Settings in a newly created account, when I click Save, language changes are seen immediately.

[tuxpiper]

@Angamanga while running smoke tests, i noticed the following:
From an old account, when I change language from General settings, language changes don't come into effect when I click Save, I have to log out of the account. When logged out, then the new language changes are seen.
However, I created a new account. When I change language from General Settings in a newly created account, when I click Save, language changes are seen immediately.

I think this more or less matches the expected behavior I read from the code: if the user account has a language preference, that should always take precedence over the language chosen in "General settings". (I'm assuming the "old account" had some language preference saved in the database)

[Angamanga]

@tuxpiper @Obadha2 Yep, that is the expected behaviour right now at least, but it is confusing. There is a wip pr that deals with it, but its abandoned (by me) right now. Plan to take up work on it.