Limit snippet characters

[freedompraise]

Description

Added functionality to ensure the snippet field has a limit.
The limit used was 255 other suggestions would be appreciated.
For more detail, it closes #365

Changes Made

• Added new feature
• Fixed bug
• Refactored code
• Other (please describe):

Test Plan

No test plan yet, till the logic is confirmed

Checklist

• I have read the contributing guidelines
• I have added tests to cover my changes and they all pass in addition to the existing tests.
• I have added documentation for my changes (if appropriate)

[jsolly]

Looks good to me. I added a small CSS update so the error message looks red when there are too many characters.

Could you add a test for adding a snippet that is too long and it is blocked?

[jsolly]

Add one test for this

[freedompraise]

Add one test for this

Alright

[jsolly]

I made the following changes.
1 - Move the snippet validation logic to the Post forms.py file. This way we can add the validator without a new migration.
2 - Created a new test_validators.py testfile
3 - Refactored the snippet validator so max_length can be a dependency injection. We want to minimize using globals so the test functions can manipulate this value if they need to.

[jsolly]

@freedompraise unfortunately, I think the Snippet validator needs more work. I was able to get it to block me when I was well under 400 characters. This is because the text I copy/pasted in had formatting. See the following GIF

Here is a link to the video if that GIF doesn't render.

Also added a failing test for you that contains the HTML shown in the video.

[jsolly]

Please resolve the failing text and check any other edge cases if you can find them.

[jsolly]

If you applied that migration you had, you'll have to roll that back because I removed it.

[freedompraise]

Please resolve the failing text and check any other edge cases if you can find them.

I'll look into it

[jsolly]

Nice work @freedompraise. Merging

[jsolly]

Approve!