feat: making the color of the email button variable

[DeimerM]

Hi team, I hope you all are doing great !!

This PR is intended to make the color of the emails button variable, this so that there is consistency with the colors that are placed when configuring these settings "email_button__color" and "email_button__background", since when configuring this setting in our tenants it remains as follows.

The code that is currently responsible for configuring these colors can be found below.

ednx-saas-themes/edx-platform/bragi/lms/templates/ace_common/edx_ace/common/return_to_course_cta.html

Lines 21 to 36 in e7f864f

	style="
	color: {{ EMAIL_COLORS.email_button__color|default:"#4c4b4b" }};
	text-decoration: none;
	border-radius: 4px;
	-webkit-border-radius: 4px;
	-moz-border-radius: 4px;
	background-color: {{ EMAIL_COLORS.email_button__background|default:"#2e9fd8" }};
	border-top: 12px solid {{ EMAIL_COLORS.email_button__border|default:"#2e9fd8" }};
	border-bottom: 12px solid {{ EMAIL_COLORS.email_button__border|default:"#2e9fd8" }};
	border-right: 50px solid {{ EMAIL_COLORS.email_button__border|default:"#2e9fd8" }};
	border-left: 50px solid {{ EMAIL_COLORS.email_button__border|default:"#2e9fd8" }};
	display: inline-block;
	">
	{# old email clients require the use of the font tag :( #}
	<font color="{{ EMAIL_COLORS.email_button__color|default:"#4c4b4b" }}"><b>{{ course_cta_text }}</b></font>
	</a>

How to test

1. Add the following setting in your site's tenant config.

"EMAIL_COLORS": {
    "email_button__background": "#000000",
    "email_button__color": "#ffffff"
}

2. Send emails from your site to test the button looks great.

[bra-i-am]

Hi @DeimerM, I hope you are doing great!

Could you please give me an update about this PR?

Thank you!! :D