Admin: Use "Log" over "Sign"

[machikoyasuda]

This ticket is still Needs shaping, and is a placeholder for @indexing to confirm which direction we're going, copy-wise, update it on Miro, before devs can work on it.

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The Administrator app (which encompasses everything under /admin/ and /in_person/) should use the term Log in over the term (Sign).

Currently, Sign is used in two places in the Admin app:

• the agency-base header override uses Sign

• the Google SSO button uses Sign

This ticket is to change it in both of these places.

• Django SSO offers a variable to do it: https://megalus.github.io/django-google-sso/customize/#the-button-text
• And the header can be changed in this template file here:

  benefits/benefits/templates/admin/agency-base.html

  Line 51 in feb06d2

  <button type="submit" class="border-0">Sign out</button>

Why?

It's good to be consistent, and the Admin app is using the two terms interchangeably currently. For example, when I click Sign out, it takes me to this page:

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Note: The Benefits app itself uses Sign and Log interchangeably, but this PR is only about Admin.

[machikoyasuda]

cc @indexing