### What is the problem?
It is possible to pass an arbitrary value to the limit parameter in `TagsController#search`, and have it flow through `DiscourseTagging.filter_allowed_tags` where it will raise an error deep in the database driver. MiniSql ensures there's no injection happening, but that ultimately results in an invalid query.
### How does this fix it?
This change checks more strictly that the parameter can be cleanly converted to an integer by replacing the loose `#to_i` conversion semantics with the stronger `Kernel#Integer` ones.
**Example:**
```ruby
"1; SELECT 1".to_i
#=> 1
Integer("1; SELECT 1")
#=> ArgumentError
```
As part of the change, I also went ahead to disallow a limit of "0", as that doesn't seem to be a useful option. Previously only negative limits were disallowed.
07f87ff7a8