Query MX records during provider autoconfiguration

Previously MX records were queried only for OAuth 2 configuration and
did not affect the list of servers tried. User was required to manually
configure the servers for Google Workspace (former GSuite) domains.

Now MX records are queried during configuration. If provider is found in
offline database, its ID, corresponding to the filename, is saved as
`configured_provider`.

`configured_provider` is also set during database migration if email
address uses the domain from the provider database, but no MX querying
is done.

src/provider/update.py

@@ -8,7 +8,8 @@ import datetime
 
 out_all = ""
 out_domains = ""
-domains_dict = {}
+out_ids = ""
+domains_set = set()
 
 def camel(name):
     words = name.split("_")
@@ -22,15 +23,19 @@ def cleanstr(s):
     return s
 
 
+def file2id(f):
+    return os.path.basename(f).replace(".md", "")
+
+
 def file2varname(f):
-    f = f[f.rindex("/")+1:].replace(".md", "")
+    f = file2id(f)
     f = f.replace(".", "_")
     f = f.replace("-", "_")
     return "P_" + f.upper()
 
 
 def file2url(f):
-    f = f[f.rindex("/")+1:].replace(".md", "")
+    f = file2id(f)
     f = f.replace(".", "-")
     return "https://providers.delta.chat/" + f
 
@@ -61,14 +66,16 @@ def process_data(data, file):
         if domain == "" or domain.count(".") < 1 or domain.lower() != domain:
             raise TypeError("bad domain: " + domain)
 
-        global domains_dict
-        if domains_dict.get(domain, False):
+        global domains_set
+        if domain in domains_set:
             raise TypeError("domain used twice: " + domain)
-        domains_dict[domain] = True
+        domains_set.add(domain)
 
         domains += "    (\"" + domain + "\", &*" + file2varname(file) + "),\n"
         comment += domain + ", "
 
+    ids = ""
+    ids += "    (\"" + file2id(file) + "\", &*" + file2varname(file) + "),\n"
 
     server = ""
     has_imap = False
@@ -115,6 +122,7 @@ def process_data(data, file):
     after_login_hint = cleanstr(data.get("after_login_hint", ""))
     if (not has_imap and not has_smtp) or (has_imap and has_smtp):
         provider += "static " + file2varname(file) + ": Lazy<Provider> = Lazy::new(|| Provider {\n"
+        provider += "    id: \"" + file2id(file) + "\",\n"
         provider += "    status: Status::" + status + ",\n"
         provider += "    before_login_hint: \"" + before_login_hint + "\",\n"
         provider += "    after_login_hint: \"" + after_login_hint + "\",\n"
@@ -132,13 +140,14 @@ def process_data(data, file):
         raise TypeError("status PREPARATION or BROKEN requires before_login_hint: " + file)
 
     # finally, add the provider
-    global out_all, out_domains
+    global out_all, out_domains, out_ids
     out_all += "// " + file[file.rindex("/")+1:] + ": " + comment.strip(", ") + "\n"
 
     # also add provider with no special things to do -
     # eg. _not_ supporting oauth2 is also an information and we can skip the mx-lookup in this case
     out_all += provider
     out_domains += domains
+    out_ids += ids
 
 
 def process_file(file):
@@ -172,10 +181,14 @@ if __name__ == "__main__":
 
     process_dir(sys.argv[1])
 
-    out_all += "pub static PROVIDER_DATA: Lazy<HashMap<&'static str, &'static Provider>> = Lazy::new(|| [\n"
+    out_all += "pub(crate) static PROVIDER_DATA: Lazy<HashMap<&'static str, &'static Provider>> = Lazy::new(|| [\n"
     out_all += out_domains;
     out_all += "].iter().copied().collect());\n\n"
 
+    out_all += "pub(crate) static PROVIDER_IDS: Lazy<HashMap<&'static str, &'static Provider>> = Lazy::new(|| [\n"
+    out_all += out_ids;
+    out_all += "].iter().copied().collect());\n\n"
+
     now = datetime.datetime.utcnow()
     out_all += "pub static PROVIDER_UPDATED: Lazy<chrono::NaiveDate> = "\
                "Lazy::new(|| chrono::NaiveDate::from_ymd("+str(now.year)+", "+str(now.month)+", "+str(now.day)+"));\n"