Support sweet_xml 0.7

[23Skidoo]

sweet_xml 0.7 was released in July 2021. There are already some libraries like ex_aws that specify sweet_xml ~> 0.7 in their dependencies, which results in an error when ex_aws and soap are used together.

[eckmanca-caremore]

This is an important change that needs to be done. There is a high vulnerability security flaw with older versions of sweet_xml.
https://security.snyk.io/vuln/SNYK-HEX-SWEETXML-1088046.
Even though SNYK says no fixed, it has been fixed with sweet_xml 7, see kbrw/sweet_xml#71

[eckmanca-caremore]

FYI. Switching to use Hex instead of Github works for allowing the override to work.
Change:
{:soap, git: "https://github.com/potok-digital/soap", tag: "master"}
to:
{:soap, "~> 1.1.0"}

[cgarvis]

This shouldn't be an issue due to #97