Thumbor URL chaining filters does not work since v4.2

[Furytron]

Describe the bug
Thumbor URLs cannot chain filters. in version 3.1.1 you could chain the filters, now since v4.2 you cannot chain them.
See Thumbor documentation, which has lots of examples of chained filters: https://thumbor.readthedocs.io/en/latest/filters.html#how-filters-work

If lots of filters are used, the URLs can become long and ugly.

To Reproduce

1. In v3.1.1 you can use the following url: https://example.cloudfront.net/filters:grayscale():blur(20)/myimage.jpg
2. Since v4.2 you cannot use the following url: https://example.cloudfront.net/filters:grayscale():blur(20)/myimage.jpg, the URL must be: https://example.cloudfront.net/filters:grayscale()/filters:blur(20)/myimage.jpg. Where there is the text "filters:" for each filter.

Expected behavior
Should support chaining the filters: /filters:grayscale():blur(20):rotate(90)/.
Since changes this may break existing filters, you will likely need to support both chaining filters, and the current broken way.
It is still broken in v6.0.

Please complete the following information about the solution:

• Version: v4.2
• Region: all
• Was the solution modified from the version published on this repository?
• If the answer to the previous question was yes, are the changes available on GitHub?
• Have you checked your service quotas for the sevices this solution uses?
• Were there any errors in the CloudWatch Logs?

Screenshots
Working image, without chained filters:

Not working image, with chained filters

Additional context
This is an issue that was already logged but mistakenly closed: #187

[fisenkodv]

@Furytron thank you for your feedback. We will look into it and add it to our backlog.

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[Furytron]

keep open

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[Furytron]

Keep open... again

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[dougtoppin]

addressed with v6.2.4