Fix usage with Ecto 3.12

[Gladear]

Fixes #108

• update Ecto to 3.12, force its usage, this change isn't going to be retrocompatible
• use Ecto's new :parametrized representation
• update changelog to reflect this change. Should this be noted down as breaking change?

[lleger]

Thanks for this PR, can confirm it fixes the issue upgrading from Ecto 3.11.3 → 3.12.0.

[lleger]

Just wanted to call out, I was looking at the issue that introduced this change here (elixir-ecto/ecto#4419), eventually they added Ecto.Type.parameterized?/2 to help, specifically mentioning this code: elixir-ecto/ecto#4488

[coveralls]

Pull Request Test Coverage Report for Build 793aece67eda84cba2fbb70cd9aab638757452d4-PR-109

Details

• 2 of 3 (66.67%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 83.008%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/polymorphic_embed.ex	2	3	66.67%

Files with Coverage Reduction	New Missed Lines	%
lib/polymorphic_embed.ex	1	82.04%

Totals
Change from base Build 68e54e0df69da37bc48bdc160c77579a59adbdb1:	0.0%
Covered Lines:	298
Relevant Lines:	359

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 793aece67eda84cba2fbb70cd9aab638757452d4-PR-109

Details

• 2 of 3 (66.67%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 83.008%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/polymorphic_embed.ex	2	3	66.67%

Files with Coverage Reduction	New Missed Lines	%
lib/polymorphic_embed.ex	1	82.04%

Totals
Change from base Build 68e54e0df69da37bc48bdc160c77579a59adbdb1:	0.0%
Covered Lines:	298
Relevant Lines:	359

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 793aece67eda84cba2fbb70cd9aab638757452d4-PR-109

Details

• 2 of 3 (66.67%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 83.008%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/polymorphic_embed.ex	2	3	66.67%

Files with Coverage Reduction	New Missed Lines	%
lib/polymorphic_embed.ex	1	82.04%

Totals
Change from base Build 68e54e0df69da37bc48bdc160c77579a59adbdb1:	0.0%
Covered Lines:	298
Relevant Lines:	359

---

💛 - Coveralls