Client creation must not be blocking

[tobiasKaminsky]

Ref: #6214

• streamline OwnCloudClientManager and OwnCloudClientFactory

[ezaquarii]

The issue is with AccountManager.blockingGetAuthToken() request that potentially goes over the network.

Generally, getAuthToken() API is asynchronous because it supports use cases when user is prompted via notification to provide credentials.

     * <p>In that case, you may need to wait until the user responds, which
     * could take hours or days or forever.  When the user does respond and
     * supply a new password, the account manager will broadcast the
     * {@link #LOGIN_ACCOUNTS_CHANGED_ACTION} Intent and
     * notify {@link OnAccountsUpdateListener} which applications can
     * use to try again.

If we don't use this functionality (and the use of a blocking getter suggests tells me that this is the case), then we probably already get the token from cache. In such case, we need to store it differently.

Looks like something that should be provided via UserAccountManager.

[tobiasKaminsky]

In our case the password is an app token, which is retrieved during setup and then never can change again.
So for us there will never be a blocking (to retrieve a new password) nor there should be any delay (as the "password" is always cached in AccountManager).

We could use AccountManager.peekAuthToken(…)
I guess we do not need to change it for legacy owncloudClient, but for NextcloudClient.

[tobiasKaminsky]

This is done for new NextcloudClient.
For old ownCloudClient we will not change it.