2952/proxy (#2961)

* replace hard-coded strings with existing constants

* proxy port

* * custom proxy port and hostname inputs
* typesafety, refactor, linting, unit tests

* relocate ProxyConfiguration in app structure

* remove unused editTextPreference fn

* allow preference category to have no title

* refactor proxy prefs hierarchy/dependency

app/src/test/java/com/keylesspalace/tusky/entity/ProxyConfigurationTest.kt

@@ -0,0 +1,46 @@
+package com.keylesspalace.tusky.entity
+
+import com.keylesspalace.tusky.settings.ProxyConfiguration
+import org.junit.Assert
+import org.junit.Test
+
+class ProxyConfigurationTest {
+    @Test
+    fun `serialized non-int is not valid proxy port`() {
+        Assert.assertFalse(ProxyConfiguration.isValidProxyPort("should fail"))
+        Assert.assertFalse(ProxyConfiguration.isValidProxyPort("1.5"))
+    }
+
+    @Test
+    fun `number outside port range is not valid`() {
+        Assert.assertFalse(ProxyConfiguration.isValidProxyPort("${ProxyConfiguration.MIN_PROXY_PORT - 1}"))
+        Assert.assertFalse(ProxyConfiguration.isValidProxyPort("${ProxyConfiguration.MAX_PROXY_PORT + 1}"))
+    }
+
+    @Test
+    fun `number in port range, inclusive of min and max, is valid`() {
+        Assert.assertTrue(ProxyConfiguration.isValidProxyPort(ProxyConfiguration.MIN_PROXY_PORT))
+        Assert.assertTrue(ProxyConfiguration.isValidProxyPort(ProxyConfiguration.MAX_PROXY_PORT))
+        Assert.assertTrue(ProxyConfiguration.isValidProxyPort((ProxyConfiguration.MIN_PROXY_PORT + ProxyConfiguration.MAX_PROXY_PORT) / 2))
+    }
+
+    @Test
+    fun `create with invalid port yields null`() {
+        Assert.assertNull(ProxyConfiguration.create("hostname", ProxyConfiguration.MIN_PROXY_PORT - 1))
+    }
+
+    @Test
+    fun `create with invalid hostname yields null`() {
+        Assert.assertNull(ProxyConfiguration.create(".", ProxyConfiguration.MIN_PROXY_PORT))
+    }
+
+    @Test
+    fun `create with valid hostname and port yields the config object`() {
+        Assert.assertTrue(ProxyConfiguration.create("hostname", ProxyConfiguration.MIN_PROXY_PORT) is ProxyConfiguration)
+    }
+
+    @Test
+    fun `unicode hostname allowed`() {
+        Assert.assertTrue(ProxyConfiguration.create("federação.social", ProxyConfiguration.MIN_PROXY_PORT) is ProxyConfiguration)
+    }
+}