This commit operates at three levels of abstraction:
1. We want to prevent user history rows from being unbounded in size.
This commit adds rails validations to limit the sizes of columns on
user_histories,
2. However, we don't want to prevent certain actions from being
completed if these columns are too long. In those cases, we truncate
the values that are given and store the truncated versions,
3. For endpoints that perform staff actions, we can further control
what is permitted by explicitly validating the params that are given
before attempting the action,
This commit contains 3 features:
- FEATURE: Allow downloading watched words
This introduces a button that allows admins to download watched words per action in a `.txt` file.
- FEATURE: Allow clearing watched words in bulk
This adds a "Clear All" button that clears all deleted words per action (e.g. block, flag etc.)
- FEATURE: List all blocked words contained in the post when it's blocked
When a post is rejected because it contains one or more blocked words, the error message now lists all the blocked words contained in the post.
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This also changes the format of the file for importing watched words from `.csv` to `.txt` so it becomes inconsistent with the extension of the file when watched words are exported.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
