WIP: [API][Tax Rate] Add admin tax rates api

[diimpp]

Q	A
Branch?	1.13
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Related tickets	partially #11250
License	MIT

• adding_tax_rate.feature
• deleting_multiple_tax_rates.feature
• deleting_tax_rate.feature
• editing_tax_rate.feature
• tax_rates_filtration / filtering_tax_rates_by_end_date.feature
• tax_rates_filtration / filtering_tax_rates_by_start_date.feature
• tax_rate_unique_code_validation.feature
• tax_rate_validation.feature
• ???

[jakubtobiasz]

Hi @diimpp!
I haven't noticed this PR earlier, but there's a new PR #14811 (which is a successor of #11884). I believe we can close this one, but still thanks for your work :).