Fixes product validation on create. Fixes #5588
Remove file that shouldnt exist.
Give spec correct title.

fixes #5614
Update contributing in readme.
Allow Admins To Flush Rails Cache
fixes #5615
Check for Deleted Variants In Line Items

me fail english, that umpossible

change is_removed to is_destroyed

fixes #5611
Fix & Use NotImplementedError.
bold you
No longer true.
rename the IncompleteReimbursement to be extactly what it is.
fix typo on api payments_controller#new
[backend] Hiding option values handle if object is not persisted

[backend] @option_type.option_values is always set. No need to verify it emptiness

[backend] Hiding the handle of option values if object is not persisted

Fixes #5617
Fixes #4836
Add actionable? to Promotion::Rules::Taxon

Fixes #5621
refs #4477
support callbacks on clear cache, support custom callbacks

Fixes #5623
enable houndci for PR's
add link to new s3 documentation in the heroku deployment guide

Closes #5641
Introduce DisplayMoney class mixin to clean up display_* method model logic.

There are a lot of model-level methods named display_ that just wrap a
numeric in a Spree::Money object. Rather than taking up space and mental
overhead in the models, this class mixin allows for defining of those
desired display_methods in a tidier way (with some configuration), in an effort to make some of
these models smaller and easier to reason about.

Closes #5640
Validate uniqueness of OptionType#name. Fixes #5629
Validate uniqueness of OptionValue#name. Fixes #5630
Sequence factories for uniqueness. refs #5629