[FEAT] Add produce messages

[vinijabes]

Description

Add produce message in flow protocol

Motivation and Context

It is needed a way of publishing new messages in a channel trough client interface.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[codecov]

Codecov Report

Merging #23 (711d798) into main (10dfaca) will decrease coverage by 1.41%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
- Coverage   56.81%   55.39%   -1.42%     
==========================================
  Files          20       20              
  Lines         822      843      +21     
==========================================
  Hits          467      467              
- Misses        355      376      +21     

Impacted Files	Coverage Δ
packline/src/main.rs	0.00% <0.00%> (ø)
packline_cli/src/client.rs	0.00% <0.00%> (ø)
packline_flow/src/connector/mod.rs	0.00% <0.00%> (ø)
packline_flow/src/messages/mod.rs	0.00% <0.00%> (ø)

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