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 56.00000% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.26%. Comparing base (9f67b1c) to head (df16d87).

Files with missing lines	Patch %	Lines
src/main.rs	25.00%	12 Missing ⚠️
src/config.rs	80.00%	6 Missing ⚠️
src/handlers.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #105      +/-   ##
==========================================
+ Coverage   51.86%   54.26%   +2.39%     
==========================================
  Files          14       14              
  Lines         750      774      +24     
==========================================
+ Hits          389      420      +31     
+ Misses        361      354       -7     

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