Add documentation for populating relations with GraphQL API

docusaurus/docs/cms/api/graphql/guides/populate.md

@@ -0,0 +1,128 @@
+# Populate Relations with GraphQL API
+
+The GraphQL API in Strapi allows you to fetch related data along with your main query. This guide explains how to use the `populate` parameter to include related content in your GraphQL queries.
+
+## Basic Usage
+
+When querying a content type, you can use the `populate` parameter to include related fields. The `populate` parameter accepts a string or an array of strings representing the relation fields you want to include.
+
+```graphql
+query {
+  restaurants {
+    data {
+      id
+      attributes {
+        name
+        description
+        categories {
+          data {
+            id
+            attributes {
+              name
+            }
+          }
+        }
+      }
+    }
+  }
+}
+```
+
+In this example, the `categories` field is automatically populated because it's included in the query.
+
+## Deep Population
+
+For nested relations, you can use dot notation to populate fields deeper in the relation chain.
+
+```graphql
+query {
+  restaurants {
+    data {
+      id
+      attributes {
+        name
+        categories {
+          data {
+            id
+            attributes {
+              name
+              subcategories {
+                data {
+                  id
+                  attributes {
+                    name
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
+```
+
+This query will populate the `categories` field for restaurants and the `subcategories` field for each category.
+
+## Populate Media Fields
+
+Media fields can be populated just like other relations:
+
+```graphql
+query {
+  restaurants {
+    data {
+      id
+      attributes {
+        name
+        cover {
+          data {
+            id
+            attributes {
+              url
+              alternativeText
+            }
+          }
+        }
+      }
+    }
+  }
+}
+```
+
+## Populate Dynamic Zones
+
+For dynamic zones, you need to use fragments to specify which fields to return for each possible component:
+
+```graphql
+query {
+  articles {
+    data {
+      id
+      attributes {
+        title
+        content {
+          __typename
+          ... on ComponentTextText {
+            text
+          }
+          ... on ComponentMediaImage {
+            image {
+              data {
+                attributes {
+                  url
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
+```
+
+Remember that the GraphQL API automatically includes the fields you request in your query, so explicit use of a `populate` parameter is not necessary. Simply including the relation fields in your query structure will populate them in the response.
+
+By using these population techniques, you can efficiently retrieve related data in a single GraphQL query, reducing the number of API calls needed and improving your application's performance.