Pull request: all: add $dnsrewrite handling

Merge in DNS/adguard-home from 2102-dnsrewrite to master

Updates #2102.

Squashed commit of the following:

commit 8490fc18179d38c4b162ff9b257fea1f8535afbd
Merge: d9448ddca e7f7799b3
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Dec 21 16:44:00 2020 +0300

    Merge branch 'master' into 2102-dnsrewrite

commit d9448ddca6d4ef3635d767e3e496e44c35d3fc6e
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Dec 21 15:44:54 2020 +0300

    querylog: support dnsrewrite rules

commit 40aa5d30acddf29fb90d249d8806941c6e1915a4
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Dec 18 19:27:40 2020 +0300

    all: improve documentation

commit f776a0cd63b1640ba1e5210d9301e2a2801fd824
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Dec 18 19:09:08 2020 +0300

    dnsfilter: prevent panics, improve docs

commit e14073b7500d9ed827a151c5b8fb863c980c10e8
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Dec 4 15:51:02 2020 +0300

    all: add $dnsrewrite handling

openapi/openapi.yaml

@@ -523,7 +523,7 @@
         Reload filtering rules from URLs.  This might be needed if new URL was
         just added and you dont want to wait for automatic refresh to kick in.
         This API request is ratelimited, so you can call it freely as often as
-        you like, it wont create unneccessary burden on servers that host the
+        you like, it wont create unnecessary burden on servers that host the
         URL.  This should work as intended, a `force` parameter is offered as
         last-resort attempt to make filter lists fresh.  If you ever find
         yourself using `force` to make something work that otherwise wont, this
@@ -1246,7 +1246,7 @@
       'properties':
         'reason':
           'type': 'string'
-          'description': 'DNS filter status'
+          'description': 'Request filtering status.'
           'enum':
           - 'NotFilteredNotFound'
           - 'NotFilteredWhiteList'
@@ -1257,7 +1257,9 @@
           - 'FilteredInvalid'
           - 'FilteredSafeSearch'
           - 'FilteredBlockedService'
-          - 'ReasonRewrite'
+          - 'Rewrite'
+          - 'RewriteEtcHosts'
+          - 'DNSRewriteRule'
         'filter_id':
           'deprecated': true
           'description': >
@@ -1284,12 +1286,12 @@
           'description': 'Set if reason=FilteredBlockedService'
         'cname':
           'type': 'string'
-          'description': 'Set if reason=ReasonRewrite'
+          'description': 'Set if reason=Rewrite'
         'ip_addrs':
           'type': 'array'
           'items':
             'type': 'string'
-          'description': 'Set if reason=ReasonRewrite'
+          'description': 'Set if reason=Rewrite'
     'FilterRefreshResponse':
       'type': 'object'
       'description': '/filtering/refresh response data'
@@ -1648,7 +1650,7 @@
             '$ref': '#/components/schemas/ResultRule'
         'reason':
           'type': 'string'
-          'description': 'DNS filter status'
+          'description': 'Request filtering status.'
           'enum':
           - 'NotFilteredNotFound'
           - 'NotFilteredWhiteList'
@@ -1659,7 +1661,9 @@
           - 'FilteredInvalid'
           - 'FilteredSafeSearch'
           - 'FilteredBlockedService'
-          - 'ReasonRewrite'
+          - 'Rewrite'
+          - 'RewriteEtcHosts'
+          - 'DNSRewriteRule'
         'service_name':
           'type': 'string'
           'description': 'Set if reason=FilteredBlockedService'