diff --git a/composer.json b/composer.json
index e5ddb75..d107cf9 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
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-        "sabre/dav": "~3.2.3",
+        "sabre/dav"     : "~4.0.2",
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diff --git a/composer.lock b/composer.lock
index 57bb882..09e609e 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
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@@ -140,16 +140,16 @@
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+            "version": "2.13.1",
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-                "reference": "2a03c207d5ae038259f0abb588f64851cebdcb1a"
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@@ -173,7 +173,7 @@
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                 "laminas/laminas-session": "^2.8",
                 "laminas/laminas-uri": "^2.5",
-                "phpunit/phpunit": "^6.0.8 || ^5.7.15",
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@@ -215,7 +215,7 @@
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@@ -352,16 +352,16 @@
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+            "version": "2.31.0",
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+                "reference": "bbc0ab53f41a4c6f223c18efcdbd9bc725eb5d2d"
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-                "reference": "912dff66d2690ca66abddb9b291a1df5f371d3b4",
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@@ -418,7 +418,7 @@
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@@ -518,16 +518,16 @@
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@@ -535,27 +535,28 @@
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+                "ext-json": "*",
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-                "php": ">=5.5.0",
+                "php": ">=7.0.0",
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-                "sabre/vobject": "^4.1.0",
-                "sabre/xml": "^1.4.0"
+                "sabre/event": "^5.0",
+                "sabre/http": "^5.0",
+                "sabre/uri": "^2.0",
+                "sabre/vobject": "^4.2.0-alpha1",
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                 "monolog/monolog": "^1.18",
-                "phpunit/phpunit": "> 4.8, <6.0.0",
-                "sabre/cs": "^1.0.0"
+                "phpunit/phpunit": "^6"
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+                "ext-imap": "*",
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@@ -563,11 +564,6 @@
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@@ -597,28 +593,28 @@
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+                "php": "^7.1"
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-                "phpunit/phpunit": "*",
-                "sabre/cs": "~0.0.4"
+                "friendsofphp/php-cs-fixer": "~2.16.1",
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@@ -648,38 +644,42 @@
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                 "EventEmitter",
                 "async",
+                "coroutine",
+                "eventloop",
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-            "time": "2015-11-05T20:14:39+00:00"
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+                "ext-curl": "*",
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-                "php": ">=5.4",
-                "sabre/event": ">=1.0.0,<4.0.0",
-                "sabre/uri": "~1.0"
+                "php": "^7.1",
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+                "friendsofphp/php-cs-fixer": "~2.16.1",
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@@ -710,28 +710,28 @@
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+            "time": "2020-01-31T20:07:09+00:00"
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-                "sabre/cs": "~1.0.0"
+                "friendsofphp/php-cs-fixer": "~2.16.1",
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@@ -761,29 +761,30 @@
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-            "time": "2017-02-20T19:59:28+00:00"
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-            "version": "4.2.2",
+            "version": "4.3.0",
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-                "sabre/xml": ">=1.5 <3.0"
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+                "friendsofphp/php-cs-fixer": "~2.16.1",
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@@ -857,20 +858,20 @@
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-            "version": "1.5.1",
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@@ -878,12 +879,12 @@
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-                "sabre/cs": "~1.0.0"
+                "friendsofphp/php-cs-fixer": "~2.16.1",
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@@ -920,7 +921,7 @@
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-            "time": "2019-01-09T13:51:57+00:00"
+            "time": "2020-01-31T18:52:58+00:00"
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@@ -1041,16 +1042,16 @@
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-            "version": "v5.0.4",
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@@ -1114,7 +1115,7 @@
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-            "time": "2020-01-21T08:40:24+00:00"
+            "time": "2020-02-04T07:41:34+00:00"
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@@ -1175,16 +1176,16 @@
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@@ -1230,7 +1231,7 @@
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@@ -1445,26 +1446,25 @@
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-                "mockery/mockery": "~1",
-                "phpunit/phpunit": "^7.0"
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@@ -1488,7 +1488,7 @@
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-            "time": "2019-08-22T18:11:29+00:00"
+            "time": "2020-02-18T18:59:58+00:00"
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