Check authentication on each page reload

### Issue type

**I'm submitting a ...** (check one with "x")

* [ ] bug report
* [X] feature request
* [ ] question about the decisions made in the repository

### Issue description

**Current behavior:**
I'm using existing `NbPasswordAuthStrategy` and after the user becomes authenticated, the auth token successfully stores in `localStorage` and persists there until explicitly loggin out. Even if I restart by backend (which is implemented in Spring with Spring security), the user is still authenticated on a frontend but gets 401 doing request to a backend.

**Expected behavior:**
I was expecting that user authority will be checked on each page reload or in some other way (making a call to some `/users/me` endpoint). Please, suggest me what is the proper way to achieve this.
**UPD** I can see someone implements this via http interceptors but maybe such behaviour could be added to a framework 'out-of-the-box'.

**Steps to reproduce:**
- Authenticate user
- Restart backend
- User token still exists in local storage

**Related code:**
I decided to try to implement custom `NbTokenStorage` and override desired methods (one of or all of `set`, `get`, `clear`) and sticked into a `get` method, where I can check if the user is still authenticated on a backend, but this requires to make an http call while method should return a token itself instead of `Observable` and it seems that I've stand on a wrong path.

### Other information:

**npm, node, OS, Browser**
```
node v16.3.0
npm 7.15.1
OS Linux (KDE Neon)
Browser: Chrome
```

**Angular, Nebular**
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```