Ziga/og fix frontend issues from workshop

[zkokelj]

Why this change is needed

In this PR I fixed a few frontend bugs and added new features:

• support for mobile (https://github.com/obscuronet/obscuro-internal/issues/2138)
• use getStorageAt instead of local storage to get userID of an user (https://github.com/obscuronet/obscuro-internal/issues/2120)
• show user ID (part of https://github.com/obscuronet/obscuro-internal/issues/2133)
• show all accounts from Metamask and display which of them are connected to the gateway

While doing this I fixed 2 bugs on OG backend:

• use address 0x0...0 for getting UserID from getStorageAt (using anything that is not an address results in Metamask error)
• allow Gateway to use defaultUser for the requests before / after joining (to avoid Metamask "infinite" loading while trying to get eth_blockNumber - especially problematic after revoking as we are calling it with userID which is not valid anymore, but is still in the rpcURL in Metamask)

What changes were made as part of this PR

Please provide a high level list of the changes made

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[tudor-malene]

lgtm

[otherview]

Minor bits.

One question, perhaps for a different PR. How does the connect to metamask process happen ? Typically there's a button for it right ?

[zkokelj]

Current version is not working in Google Chrome (changing getUserID to 0x0000000000000000000000000000000000000000 makes it work).

Even using ethers we get error:

which makes gateway useless

[otherview]

Current version is not working in Google Chrome (changing getUserID to 0x0000000000000000000000000000000000000000 makes it work).

Even using ethers we get error: which makes gateway useless

The issue is a bit hidden to be fair. It comes from infura / an rpc response, not from Metamask.
If Obscuroscan uses this method while Metamask is connected to Ethereum it gets the same response.

A try-catch seems to do the trick.

async function getUserID() {
    try {
        return await provider.send('eth_getStorageAt', ["getUserID", getRandomIntAsString(0, 1000), null])
    }catch (e) {
        console.log(e)
        return null;
    }
}