Handle duplicate image messaages

[MrOrz]

In 20220907 meeting we discussed several cases when users may submit images that is highly similar to existing images in the database.

We will use this ticket to track the issue and see if we should mitigate this issue further (such as using image hash as article hash; don't change article ID if we change hashing algorithm)

[MrOrz]

Another log: https://g0v.hackmd.io/nNjUnOgRTqOa2dDcqF67KA?view#%E9%87%8D%E8%A4%87%E5%9C%96-log

The only solution we can think of is to memorize that the user has already clicked "Yes" before.

Given the fact that the submit button action sends session ID, we probably can just store if the user has clicked submit in the current session.