[5.2] SEF: Add "Strict Routing" option

[jgerman-bot]

New language relevant PR in upstream repo: joomla/joomla-cms#43432 Here are the upstream changes:

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diff --git a/administrator/language/en-GB/plg_system_sef.ini b/administrator/language/en-GB/plg_system_sef.ini
index 6540197978992..085b81a0a0ce4 100644
--- a/administrator/language/en-GB/plg_system_sef.ini
+++ b/administrator/language/en-GB/plg_system_sef.ini
@@ -7,6 +7,8 @@ PLG_SEF_DOMAIN_DESCRIPTION="If your site can be accessed through more than one d
 PLG_SEF_DOMAIN_LABEL="Site Domain"
 PLG_SEF_INDEXPHP_DESCRIPTION="This option enables a stricter handling of 'index.php' in URLs when 'Use URL Rewriting' is enabled in Global Configuration. It will remove 'index.php' if a URL still contains it and redirect incoming requests with 'index.php' to the version without the 'index.php'."
 PLG_SEF_INDEXPHP_LABEL="Strict handling of index.php"
+PLG_SEF_STRICTROUTING_DESCRIPTION="Prevent the router from accepting a lot of URLs which are deemed as duplicates and will automatically redirect to the correct URL with a 301."
+PLG_SEF_STRICTROUTING_LABEL="Strict Routing"
 PLG_SEF_TRAILINGSLASH_DESCRIPTION="Force Joomla to only use URLs with or without trailing slash. When set, this will force the right URL with redirects and is only applied when 'Add suffix to URL' is disabled."
 PLG_SEF_TRAILINGSLASH_LABEL="Trailing slash for URLs"
 PLG_SEF_TRAILINGSLASH_OPTION_NONE="No change"
diff --git a/plugins/system/sef/sef.xml b/plugins/system/sef/sef.xml
index edecff778b910..467cac9fe0166 100644
--- a/plugins/system/sef/sef.xml
+++ b/plugins/system/sef/sef.xml
@@ -56,6 +56,19 @@
 					<option value="0">PLG_SEF_TRAILINGSLASH_OPTION_NO_SLASH</option>
 					<option value="1">PLG_SEF_TRAILINGSLASH_OPTION_SLASH</option>
 				</field>
+
+				<field
+					name="strictrouting"
+					type="radio"
+					label="PLG_SEF_STRICTROUTING_LABEL"
+					description="PLG_SEF_STRICTROUTING_DESCRIPTION"
+					layout="joomla.form.field.radio.switcher"
+					default="0"
+					filter="boolean"
+				>
+					<option value="0">JNO</option>
+					<option value="1">JYES</option>
+				</field>
 			</fieldset>
 		</fields>
 	</config>