feat: add support for SSL

[rtm-ctrlz]

Added usage of stream_context_set_option for setting SSL options.
Added tests with certificate generation and ssl-enabled configuration for RabbitMQ.
Added some configuration examples for common use cases see examples/ssl directory.
Mentioned SSL support in main README.md.

Some notes:

• RabbitMQ added sysctl format since 3.7.0, so there are both configuration file versions prior 3.7.0 and sysctl.
• Tests covers only connections, any other tests should works same way as via plain tcp.
• There is no way to detect any errors in SSL options, so in case of error we will get exception with Could not connect to... message.

Resolves #77

[WyriHaximus]

Hey thanks for taking the time to craft this extensive PR, and it looks great, there is only one change I'd would prefer: change ssl to tls where possible.

[rtm-ctrlz]

Personally, I have no objection regarding parameter name change, but this code will not look so neat:

stream_context_set_option($context, ['ssl' => $this->options['tls']])

If you are OK with that - I'll make this change.

Also, should examples/ssl, test/ssl, variables in Makefile and filenames for RabbitMQ configs (for tests and examples) directory be renamed?

[rtm-ctrlz]

See #89 ;)

[rtm-ctrlz]

Synced branch jakubkulhan/bunny:master

[WyriHaximus]

See #89 ;)

Will have a look at it tomorrow 👍 .

[WyriHaximus]

Personally, I have no objection regarding parameter name change, but this code will not look so neat:

stream_context_set_option($context, ['ssl' => $this->options['tls']])

If you are OK with that - I'll make this change.

Also, should examples/ssl, test/ssl, variables in Makefile and filenames for RabbitMQ configs (for tests and examples) directory be renamed?

Yeah this suddenly makes sense looking at #89 🤐 !

[WyriHaximus]

Comparing this with #89 made this one look less confusing regarding naming. Still would prefer TLS but this is easier to maintain 👍