Don't use hardcoded urls in mt_auth_mixin.js

[esopp]

encompass/app/mixins/mt_auth_mixin.js

Lines 8 to 23 in 985473b

	getMtSsoUrl() {
	let { host } = window.location;
	if (host === 'encompass.mathematicalthinking.org') {
	return `https://sso.mathematicalthinking.org`;
	}
	if (host === 'enc-test.mathematicalthinking.org') {
	return 'https://sso-test.mathematicalthinking.org';
	}
	if (host === 'localhost:8082') {
	return 'http://localhost:3003';
	}
	return 'http://localhost:3002';
	},

encompass/app/mixins/mt_auth_mixin.js

Lines 37 to 43 in 985473b

	getContactEmail() {
	let { host } = window.location;
	if (host === 'encompass.mathematicalthinking.org') {
	return 'encompassmath@gmail.com';
	}
	return 'encompassmathtesting@gmail.com';
	},

NOTE:
This seems like a work-around the original developer may have used because they were having trouble accessing the environment variables. Let's try to actually solve that problem, and get the SSO url (as well as the contact email) from the .env file.