Invoke a Salesforce function from Apex

[tdn_block_newsletter_subscribe title_text="Stay in touch" description="VG8gYmUgdXBkYXRlZCB3aXRoIGFsbCB0aGUgbGF0ZXN0IG5ld3MsIG9mZmVycyBhbmQgc3BlY2lhbCBhbm5vdW5jZW1lbnRzLg==" input_placeholder="Email address" tds_newsletter2-image="5" tds_newsletter2-image_bg_color="#c3ecff" tds_newsletter3-input_bar_display="row" tds_newsletter4-image="6" tds_newsletter4-image_bg_color="#fffbcf" tds_newsletter4-btn_bg_color="#f3b700" tds_newsletter4-check_accent="#f3b700" tds_newsletter5-tdicon="tdc-font-fa tdc-font-fa-envelope-o" tds_newsletter5-btn_bg_color="#000000" tds_newsletter5-btn_bg_color_hover="#4db2ec" tds_newsletter5-check_accent="#000000" tds_newsletter6-input_bar_display="row" tds_newsletter6-btn_bg_color="#da1414" tds_newsletter6-check_accent="#da1414" tds_newsletter7-image="7" tds_newsletter7-btn_bg_color="#1c69ad" tds_newsletter7-check_accent="#1c69ad" tds_newsletter7-f_title_font_size="20" tds_newsletter7-f_title_font_line_height="28px" tds_newsletter8-input_bar_display="row" tds_newsletter8-btn_bg_color="#00649e" tds_newsletter8-btn_bg_color_hover="#21709e" tds_newsletter8-check_accent="#00649e" embedded_form_code="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" descr_space="eyJhbGwiOiIxNSIsImxhbmRzY2FwZSI6IjE1In0=" tds_newsletter="tds_newsletter3" tds_newsletter3-all_border_width="0" btn_text="Sign up" tds_newsletter3-btn_bg_color="#ea1717" tds_newsletter3-btn_bg_color_hover="#000000" tds_newsletter3-btn_border_size="0" tdc_css="eyJhbGwiOnsibWFyZ2luLWJvdHRvbSI6IjAiLCJiYWNrZ3JvdW5kLWNvbG9yIjoiI2E3ZTBlNSIsImRpc3BsYXkiOiIifSwicG9ydHJhaXQiOnsiZGlzcGxheSI6IiJ9LCJwb3J0cmFpdF9tYXhfd2lkdGgiOjEwMTgsInBvcnRyYWl0X21pbl93aWR0aCI6NzY4fQ==" tds_newsletter3-input_border_size="0" tds_newsletter3-f_title_font_family="445" tds_newsletter3-f_title_font_transform="uppercase" tds_newsletter3-f_descr_font_family="394" tds_newsletter3-f_descr_font_size="eyJhbGwiOiIxMiIsInBvcnRyYWl0IjoiMTEifQ==" tds_newsletter3-f_descr_font_line_height="eyJhbGwiOiIxLjYiLCJwb3J0cmFpdCI6IjEuNCJ9" tds_newsletter3-title_color="#000000" tds_newsletter3-description_color="#000000" tds_newsletter3-f_title_font_weight="600" tds_newsletter3-f_title_font_size="eyJhbGwiOiIyMCIsImxhbmRzY2FwZSI6IjE4IiwicG9ydHJhaXQiOiIxNiJ9" tds_newsletter3-f_input_font_family="394" tds_newsletter3-f_btn_font_family="" tds_newsletter3-f_btn_font_transform="uppercase" tds_newsletter3-f_title_font_line_height="1" title_space="eyJsYW5kc2NhcGUiOiIxMCJ9"]