The code to add an oninput attribute to remove spaces and convert to lower case whenver anything is typed:

... oninput="this.value = this.value.toLowerCase().replace(/\s/g, '')

We're going to edit the signup HTML

Signup Page / account creation:  /web?debug=1#id=7066&cids=1&menu_id=43&action=30&model=ir.ui.view&view_type=form

Update this line:

input type="text" placeholder="Email" name="login" t-att-value="login" id="login" t-attf-class="form-control #{'form-control-sm' if form_small else ''}" required="required" autocomplete="username" autofocus="autofocus" autocapitalize="off"

New Code:

input type="text" name="login" t-att-value="login" id="login" class="form-control form-control-sm" autofocus="autofocus" autocapitalize="off" required="required" t-att-readonly="'readonly' if only_passwords else None" oninput="this.value = this.value.toLowerCase().replace(/\s/g, '')"

Login Page:  /web?debug=1#id=7066&cids=1&menu_id=43&action=30&model=ir.ui.view&view_type=form
Update the following code:

input type="text" placeholder="Email" name="login" t-att-value="login" id="login" t-attf-class="form-control #{'form-control-sm' if form_small else ''}" required="required" autocomplete="username" autofocus="autofocus" autocapitalize="off"

Updated code:

input type="text" placeholder="Email" name="login" t-att-value="login" id="login" t-attf-class="form-control #{'form-control-sm' if form_small else ''}" required="required" autocomplete="username" autofocus="autofocus" autocapitalize="off" oninput="this.value = this.value.toLowerCase().replace(/\s/g, '')"

This will work for all new logins.  However if you already have mixed-case email addresses, you may run into an issue.  I've seen an addon to go through existing data sets to rectify this. 

Hope this helps someone.