Use __all__ to exclude fields from all elements of a list/tuple of submodels. Raise more informative TypeError when passing bad exclude kwargs.

[masalim2]

Change Summary

1. Raise TypeError in pydantic.utils.ValueItems when value is a list or tuple and the provided exclusion dict is not keyed by index.
2. Add cautionary sentence to the Advanced include and exclude section of docs to point out correct usage of exclude in the following example.
3. Use '__all__' keyword to exclude fields from all elements of a sequence of submodels or dicts.

Related issue number

This PR addresses a couple of my comments in #1283 -- adding a more detailed TypeError and a sentence pointing out the subtle example of correct usage. Some logic has been added to enable usage of '__all__' in the exclude kwarg of model export methods.

Checklist

• Unit tests for the changes exist
• Tests pass on CI and coverage remains at 100%
• Documentation reflects the changes where applicable
• changes/<pull request or issue id>-<github username>.md file added describing change
  (see changes/README.md for details)

[codecov]

Codecov Report

Merging #1286 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1286   +/-   ##
=======================================
  Coverage   99.89%   99.89%           
=======================================
  Files          21       21           
  Lines        3713     3725   +12     
  Branches      731      736    +5     
=======================================
+ Hits         3709     3721   +12     
  Misses          2        2           
  Partials        2        2           

Impacted Files	Coverage Δ
pydantic/utils.py	98.98% <100.00%> (+0.06%)	⬆️

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[masalim2]

Thanks for reviewing! Addressed all but the last question in the last commit.

[samuelcolvin]

looks good, I've just realised we should talk about and test fo dictionaries as well as sub-models

[masalim2]

Done. Should I rebase on upstream master to resolve conflicts, or do you want to handle that yourself?

[samuelcolvin]

I've made a few tiny tweaks to avoid wasting your time with another review. Will merge once tests pass.