fix: do not save "Automatic" into configured_imap_certificate_checks

configured_imap_certificate_checks=0 means
accept invalid certificates unless provider database
says otherwise or SOCKS5 is enabled.
It should not be saved into the database anymore.

This bug was introduced in
<https://github.com/deltachat/deltachat-core-rust/pull/5854>
(commit 6b4532a08e)
and affects released core 1.142.4, 1.142.5 and 1.142.6.

Fix reverts faulty fix from
<https://github.com/deltachat/deltachat-core-rust/pull/5886>
(commit a268946f8d)
which changed the way configured_imap_certificate_checks=0
is interpreted and introduced problems
for existing setups with configured_imap_certificate_checks=0:
<https://github.com/deltachat/deltachat-core-rust/issues/5889>.

Existing test from previous fix is not reverted
and still applies.
Regression test is added to check that
configured_imap_certificate_checks
is not "0" for new accounts.

deltachat-rpc-client/tests/test_something.py

@@ -635,3 +635,24 @@ def test_get_http_response(acfactory):
     http_response = alice._rpc.get_http_response(alice.id, "https://example.org")
     assert http_response["mimetype"] == "text/html"
     assert b"<title>Example Domain</title>" in base64.b64decode((http_response["blob"] + "==").encode())
+
+
+def test_configured_imap_certificate_checks(acfactory):
+    alice = acfactory.new_configured_account()
+    configured_certificate_checks = alice.get_config("configured_imap_certificate_checks")
+
+    # Certificate checks should be configured (not None)
+    assert configured_certificate_checks
+
+    # 0 is the value old Delta Chat core versions used
+    # to mean user entered "imap_certificate_checks=0" (Automatic)
+    # and configuration failed to use strict TLS checks
+    # so it switched strict TLS checks off.
+    #
+    # New versions of Delta Chat are not disabling TLS checks
+    # unless users explicitly disables them
+    # or provider database says provider has invalid certificates.
+    #
+    # Core 1.142.4, 1.142.5 and 1.142.6 saved this value due to bug.
+    # This test is a regression test to prevent this happening again.
+    assert configured_certificate_checks != "0"