One time keys upload can try to upload the same key again

[manuroe]

There is probably a bad management of network errors when uploading them.

The server answers:

{
    errcode = "M_UNKNOWN";
    error = "One time key signed_curve25519:AAABVQ already exists. Old key: ...."
}

The application is then stuck in this configuration and cannot upload new keys.
The error even pops up as a modal if you clear the cache from app settings.

[manuroe]

This is not a network management error. I don't know the reason of this error yet but it leads to UISIs.

The reason is that the SDK keeps trying to upload its local OTKs and getting the same error until the existing OTK published on the server is consumed. Then, the upload succeeds and an OTK with an already used ID is published on the server.
The next device that will try to establish a session with this device will fail with a OLM error BAD_MESSAGE_KEY_ID.

[manuroe]

This issue is a bit hard to reproduce outside a real usage for severals days. The quickest way I found is to:

1. Hack those methods:

- (void)markOneTimeKeysAsPublished
{
    [olmAccount markOneTimeKeysAsPublished];

    //[store storeAccount:olmAccount];
}

- (void)generateOneTimeKeys:(NSUInteger)numKeys
{
    [olmAccount generateOneTimeKeys:1];

    //[store storeAccount:olmAccount];
}

2. Log on a new device
3. Restart the app

As we upload only 1 OTK at the time, at the step #3, we will try to upload a key with an existing id.

[manuroe]

Should be fixed by the merged PR.