Ensure public address always present

[tpoliaw]

The address where the glazed service is accessible may be different from
the address to which it is bound. Making both fields available in the
configuration means either can be overridden but both will have sensible
defaults.

The default values are also changed

• bind_address now defaults to 127.0.0.1 instead of 0.0.0.0 so it is not
  publicly accessible
• public_address now defaults to localhost:3000 instead of defaulting to
  the same as the bind_address

The trailing slash at the end of the public address is no longer
significant and will be normalised before appending the graphql
component.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 24 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.72%. Comparing base (a2eb617) to head (7c5812d).

Files with missing lines	Patch %	Lines
src/main.rs	0.00%	12 Missing ⚠️
src/config.rs	0.00%	10 Missing ⚠️
src/handlers.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #105      +/-   ##
==========================================
- Coverage   49.27%   48.72%   -0.55%     
==========================================
  Files          13       13              
  Lines         621      628       +7     
==========================================
  Hits          306      306              
- Misses        315      322       +7     

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