Derive Default on structs

[arlyon]

Closes #131

Note this expands the macros to support a default attribute which is passed to smart-default.

• use smart-default elsewhere in code, rather than a manual impl

[codecov]

Codecov Report

Merging #152 (6d1521c) into master (496de27) will decrease coverage by 0.42%.
The diff coverage is 0.00%.

@@            Coverage Diff            @@
##           master    #152      +/-   ##
=========================================
- Coverage    4.86%   4.43%   -0.43%     
=========================================
  Files         117     119       +2     
  Lines        9215   10102     +887     
=========================================
  Hits          448     448              
- Misses       8767    9654     +887     

Impacted Files	Coverage Δ
openapi/src/main.rs	0.00% <ø> (ø)
src/ids.rs	34.85% <0.00%> (-0.61%)	⬇️
src/params.rs	34.09% <0.00%> (-0.80%)	⬇️
src/resources/balance_transaction_ext.rs	0.00% <0.00%> (ø)
src/resources/card.rs	0.00% <0.00%> (ø)
src/resources/generated/account.rs	1.86% <0.00%> (-0.34%)	⬇️
src/resources/generated/account_link.rs	0.00% <0.00%> (ø)
src/resources/generated/alipay_account.rs	0.00% <ø> (ø)
src/resources/generated/api_errors.rs	0.00% <0.00%> (ø)
src/resources/generated/application.rs	0.00% <ø> (ø)
... and 82 more

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[FL33TW00D]

@arlyon What's left on this? anything you need a hand with?

[arlyon]

I just need to rejigger the manual default derives to use smart default where possible otherwise we're good to go. One thing is that this may lead to wacky code in certain places if you declare use ..Default:: default() and don't consider the implications. If you'd like to check over the defaults that would be nice.