Add bitbucketserver_plugin_config resource to allow managing plugins configuration.

Plugin configuration documentation.

docusaurus/docs/resource_plugin_config.md

@@ -0,0 +1,34 @@
+---
+id: bitbucketserver_plugin_config
+title: bitbucketserver_plugin_config
+---
+
+Configure plugins.
+
+## Example Usage
+
+```hcl
+resource "bitbucketserver_plugin_config" "mypluginconfig" {
+  key    = "my-plugin-key"
+  values = "{"\key\": \"value\"}"
+}
+```
+
+## Argument Reference
+
+* `key` - Required. Unique key of the plugin. This is not the same used by plugin install.
+* `values` - Required. Plugin configuration in JSON format.
+
+## Attribute Reference
+
+* `key` - Unique key of the plugin. This is not the same used by plugin install.
+* `validlicense` - Indicates if the plugins has a valid license.
+* `values` - Plugin configuration in JSON format.
+
+## Import
+
+Import a plugin config reference via the key:
+
+```
+terraform import bitbucketserver_plugin_config.mypluginkey my-plugin-key
+```