feat(elixir): add unix domain sockets transport and getting-started example

[tzumby]

Current Behavior

Currently there is no implementation of Unix Domain Socket Transports for Elixir implementation.

Proposed Changes

This PR is still Work in Progress

• [x] Prototype the unix domain sockets transport
• [x] Add examples
• [ ] Add tests
• [ ] Clean up sockets after crashes / shutdown
• [ ] Allow multiple UDS gen_tcp servers to run (currently using named processes for the Connection supervision)

       +-----------------+                                                                 
       | UDS(Supervisor) |                                                                 
       +--------/----\---+                                                                 
               /      \                                                                    
              /        \                                                                   
             /       +-----------+                                                         
            /        | Listener  --------|                                                 
           /         +-----------+       |                                                 
          /                              | Start Connection children                       
   +-----------------------+             |                                                 
   |Connection Supervisor  --------------|                                                 
   |(dynamic)              |                                                               
   +------/----------\-----+                                                               
         /            \                                                                    
        /              -\                                                                  
       /                 \                                                                 
      /                   \                                                                
+--------------------++--------------------+                                               
| Connection Process || Connection Process |                                               
|                    ||                    |                                               
| +--------+         || +--------+         |                                               
| | socket |         || | socket |         |                                               
| +--------+         || +--------+         |                                               
+--------------------++--------------------+                                               
                                                      

Checks

• [x] All commits in this Pull Request are signed and Verified by Github.
• [x] All commits in this Pull Request follow the Ockam commit message convention.
• [x] I accept the Ockam Community Code of Conduct.
• [x] I have accepted the Ockam Contributor License Agreement by adding my Git/Github details in a row at the end of the CONTRIBUTORS.csv file in a separate pull request to the build-trust/ockam-contributors repository.

[etorreborre]

Hi @tzumby I can see it has been a while since this PR has been opened. Is there anything we can do to help you finish it?

[tzumby]

Hey @etorreborre, thanks for messaging, I would love to push this over the finish line, but I'm absolutely swamped with work. If this is blocking anything maybe it makes sense that I either close it or have someone else co-author this with me ?

[etorreborre]

@tzumby no worries this is not on the critical path at the moment but we will see if we can maybe find someone to help you out with this.