Implement EPSV (Extended Passive Mode)

[veeso]

ISSUE 28 - Implement EPSV (Extended Passive Mode)

Fixes #28

Description

Implementation of EPSV according to RFC 2428, section 3. See also https://www.jscape.com/blog/what-is-the-ftp/s-epsv-command-and-when-do-you-use-it

• [x] Implemented EPSV on Sync client
• [x] Implemented EPSV on Async client
• [x] Updated suppaftp-cli to support EPSV
• [x] Updated cargo dependencies
• [x] Updated documentation to talk about EPSV

Type of change

Please select relevant options.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

Checklist

• [x] My code follows the contribution guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] My changes generate no new warnings
• [x] I formatted the code with cargo fmt
• [x] I linted my code using cargo clippy and reports no warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have introduced no C-bindings
• [x] I increased or maintained the code coverage for the project, compared to the previous commit

Acceptance tests

• [x] regression test: normal passive mode still works
• [x] I can transfer files with EPSV mode

[veeso]

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