Support for blacklisting a user network-wide

[CoconutMacaroon]

(List from here)

What does your pull request change or introduce to the project?

This PR resolves #6845 by adding support for blacklisting a user network-wide.

What is the justification for the inclusion of your Pull Request (or, what problem does it solve?)

See #6845.

Write meaningful commit messages [...]

I tried to, although I didn't include the why, seeing as it's here and in the linked issue.

Include comments in your code to help guide reviewers through what you intend for the sub-portions of your code to be doing. [...]

I've added some comments where it seemed appropriate.

Use meaningful variable names. [...]

I think I did, but I'm open to suggested changes (on anything here, of course, not just the variable names).

What testing have you done? [...]

I've updated some existing tests to handle the changed phrasing, although I haven't added tests to cover the added functionality. I've been testing my changes in this room, which includes the changes that don't have tests.

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For this PR:

• Adds the account ID to the Post class. It may be preferable to instead use the change(s) Makyen describes here instead.
• Updates addblu and rmblu text to note a network-wide blacklist.
• Change the isblu text based on if they're (a) on the site blacklist & (b) if they're on the network-wide blacklist
• Add a note in the check_if_spam function - not sure if I did that correctly
• Add a command to blacklist a user network-wide but given either a SE account link or a site profile link.

Not in this PR - these may be reasonable to implement; however, to reduce scope of this PR, I'm postponing them,

• Have isblu should list site blacklists when checking a SE account - e.g., doing !!/isblu https://stackexchange.com/users/<someone> would also list and sites that <someone> blacklisted on
• Change addblu and rmblu to note if a user is already network-wide blacklisted if changing a site blacklist

Note that I wasn't seeing the account_id with the existing filter,. I'm not sure why, so I changed it for testing, but I (or someone else) should investigate.

[danthe1st]

I guess the new commands should be added to the wiki once this PR is merged.

[CoconutMacaroon]

I guess the new commands should be added to the wiki once this PR is merged. - @danthe1st

How does this look?

!!/addnetblu <profile_URL> or !!/addnetblu <user_ID> <site_name> — Adds a user to the network-wide user-blacklist (this means that any post by this user, on any site, will be reported when scanned). Accepts either a site profile or a network profile.

!!/rmnetblu <profile_URL> or !!/rmnetblu <user_ID> <site_name> — Removes a user from the network-wide user-blacklist. Accepts either a site profile or a network profile.

[danthe1st]

This looks fine for me but I am not at all involved with maintaining anything in this repository at all.