Filtering - New blacklist type that catch all subdomains of domain

[ks129]

There is sites that have a lot of different subdomains and all of them should be banned from PyDis. We should have new blacklist that filter out all subdomains of blacklisted domains to avoid adding them one-by-one.

[MarkKoz]

I don't think it should be a separate filter. It could be integrated into the existing one. The way I envision it is that simply specifying the domain will filter all its subdomains too. This would apply to any level. So b.a.com will filter itself and any further level subdomains of it like c.b.a.com but not a.com. Granted, it would then be impossible to filter only all subdomains and not the current level. However, I don't foresee that being required.

[Shivansh-007]

This can possibly done with the help of Wolfram Alpha

1. The domain:

   

2. In the 3rd section, click Subdomains

   

[onerandomusername]

This can possibly done with the help of Wolfram Alpha

1. The domain:
   ![image](https://user-images.githubusercontent.com/69356296/114325557-5625bc00-9b4e-11eb-9ff8-8eff6ae26a93.png)

2. In the 3rd section, click **Subdomains**
   ![image](https://user-images.githubusercontent.com/69356296/114325550-4ad29080-9b4e-11eb-9ad2-b8e1097af8fd.png)

This actually can be done with dns lookup on a domain to see all domains registered under a specific domain.

Although, the best solution for this would likely be a regex checking for a subdomain.

[Akarys42]

This can possibly done with the help of Wolfram Alpha

1. The domain:
   
2. In the 3rd section, click Subdomains
   

Using our wolfram alpha credits for this sounds really silly. It isn't something that we need an external service of any kind for.

With the new filter system, we want to have a flag on each domain to say if it should flag subdomains, I think that's something we can do with a smart regex, something along the lines of ([a-zA-Z0-9]+\.)*([a-zA-Z0-9]+)\.([a-zA-Z0-9]+) with the second group being the second layer domain.

[Akarys42]

Superseded by #1530

[mbaruh]

The current system already filters subdomains, might be a by-product of one of the PRs. Going to close this for now.