add private registries access docs

Author: dobrac

template/customization/base-image.mdx

@@ -4,7 +4,7 @@ description: "How to define a base image for your template"
 icon: "1"
 ---
 
-### Creating template
+## Creating template
 
 When creating a template, you can specify options:
 
@@ -28,7 +28,7 @@ template = Template(
 
 **File ignoring**: The SDK automatically reads `.dockerignore` files and combines them with your `ignoreFilePaths`. Files matching these patterns are excluded from uploads and hash calculations.
 
-### Defining base image
+## Defining base image
 Choose from predefined base images or use custom ones:
 
 <CodeGroup dropdown>
@@ -93,7 +93,7 @@ template.from_dockerfile("FROM ubuntu:22.04\nRUN apt-get update")
 You can only call base image methods once per template. Subsequent calls will throw an error.
 </Note>
 
-### Parsing existing Dockerfiles
+## Parsing existing Dockerfiles
 
 Convert existing Dockerfiles to template format using `fromDockerfile()`:
 
@@ -134,7 +134,7 @@ template = (
 
 </CodeGroup>
 
-#### Dockerfile instructions support
+### Dockerfile instructions support
 
 | Instruction          | Supported  | Behavior                                                                                          |
 | :---                 |    :----:  | :---                                                                                              |
@@ -151,3 +151,87 @@ template = (
 <Warning>
 Multi-stage Dockerfiles are not supported.
 </Warning>
+
+## Login to private registries
+If your base image is hosted in a private registry, you can provide credentials using the following helpers:
+- General registry
+- GCP Artifact Registry
+- AWS ECR
+
+### General Registry
+
+<CodeGroup dropdown>
+
+```typescript
+Template().fromRegistry('ubuntu:22.04', {
+  username: 'user',
+  password: 'pass',
+})
+```
+
+```python
+Template().from_registry(
+    image="ubuntu:22.04",
+    username="user",
+    password="pass",
+)
+```
+
+</CodeGroup>
+
+
+### GCP Artifact Registry
+
+<CodeGroup dropdown>
+
+```typescript
+// From file path
+Template().fromGCPRegistry('ubuntu:22.04', {
+  serviceAccountJSON: './service_account.json',
+})
+
+// From object
+Template().fromGCPRegistry('ubuntu:22.04', {
+  serviceAccountJSON: { project_id: '123', private_key_id: '456' },
+})
+```
+
+```python
+# From file path
+Template().from_gcp_registry(
+    image="ubuntu:22.04",
+    service_account_json="./service_account.json",
+)
+
+# From object
+Template().from_gcp_registry(
+    image="ubuntu:22.04",
+    service_account_json={"project_id": "123", "private_key_id": "456"},
+)
+```
+
+</CodeGroup>
+
+
+### AWS ECR
+
+<CodeGroup dropdown>
+
+```typescript
+Template().fromAWSRegistry('ubuntu:22.04', {
+  accessKeyId: '123',
+  secretAccessKey: '456',
+  region: 'us-west-1',
+})
+```
+
+```python
+Template().from_aws_registry(
+    image="ubuntu:22.04",
+    access_key_id="123",
+    secret_access_key="456",
+    region="us-west-1",
+)
+```
+
+</CodeGroup>