Add setting to allow other methods to be saved as SEPA tokens

[wjrosa]

Fixes #3786

Changes proposed in this Pull Request:

This PR adds a new setting to allow merchants to control whether Bancontact and iDEAL payment methods can be saved for later purchases as SEPA Direct Debit tokens. Some merchants would avoid this behavior since the SEPA method takes too long to be identified (~8 business days).

Testing instructions

• Checkout and build this branch on your test environment (add/sepa-tokens-for-other-methods-setting)
• Connect your Stripe account
• Set your store currency to EUR
• Enable Bancontact and iDEAL
• Confirm you are able to see the new setting and it is enabled by default:

• Confirm you can disable/enable the setting and that by reloading the page the change is persisted
• As a shopper, with the setting enabled, try to add a new Bancontact method
• Confirm the method is saved

• Disable the setting and confirm you are not able to save the method anymore
• Repeat the test steps for iDEAL

---

• Covered with tests (or have a good reason not to test in description ☝️)
• Added changelog entry in both changelog.txt and readme.txt (or does not apply)
• Tested on mobile (or does not apply)

Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
• Included this PR in the Release Thread scope (or does not apply)

[annemirasol]

@wjrosa I noticed that even with the setting off, during checkout, it still asks me if I want to save my payment information:

Is that something want to hide, since it doesn't work anyways and might confuse the shopper?

[wjrosa]

@wjrosa I noticed that even with the setting off, during checkout, it still asks me if I want to save my payment information:

Is that something want to hide, since it doesn't work anyways and might confuse the shopper?

@annemirasol sorry, I forgot to mention that I fixed this issue on the other PR #3821

[annemirasol]

LGTM!

✅ With the setting turned on, I am able to save, see and use Bancontact payment tokens.
✅ With the setting turned off, I am not able to see and use saved Bancontact payment tokens.