adding docker image to reference (#74)

docs/yaml-reference/pipeline-descriptor.md

@@ -1,4 +1,4 @@
-# Pipeline YAML descriptor (quix.yaml)
+# Pipeline YAML Descriptor (quix.yaml)
 
 The `quix.yaml` file serves as the Infrastructure as Code (IaC) descriptor for a Quix project. It defines the data pipeline, including the applications (deployments) and topics that compose the pipeline. This file allows you to configure and manage your data pipeline in a declarative manner, ensuring consistency across environments.
 
@@ -57,40 +57,47 @@ deployments:
         description: This is the input topic to read data from
         required: true
         value: csv-data
+  - name: custom-service
+    image: custom-repo/my-service:1.2.3
+    deploymentType: Service
+    resources:
+      cpu: 300
+      memory: 600
+      replicas: 2
+    desiredStatus: Running
 ```
 
-**Explanation:**
+#### Explanation
 
 - **name:** The identifier for the deployment within your pipeline. It's typically a descriptive name of what the deployment does.
-
 - **application:** Specifies the name of the application or microservice to deploy. This should match the application folder where the code resides.
-  
+- **image:** The full Docker image reference (including repository and tag) to deploy. Used instead of `application` and `version` when deploying a custom Docker image.
 - **deploymentType:** Defines the type of deployment. Common types include `Service` for long-running services, `Job` for tasks that run to completion, and others as required by your architecture.
-
-- **version:** Indicates the version of the application to deploy. Using `latest` ensures that the most recent version is deployed, but this can be set to a specific version to ensure consistency. You can also use a commit reference in order to have a specific version.
-
+- **version:** Indicates the version of the application to deploy. Using `latest` ensures that the most recent version is deployed, but this can be set to a specific version to ensure consistency. You can also use a commit reference to specify a specific version.
 - **resources:** Defines the compute resources allocated to the deployment. This includes:
-    - **cpu:** The amount of CPU resources allocated (in millicores).
-    - **memory:** The amount of memory allocated (in megabytes).
-    - **replicas:** The number of instances of the application to run for scalability and fault tolerance.
-
+  - **cpu:** The amount of CPU resources allocated (in millicores).
+  - **memory:** The amount of memory allocated (in megabytes).
+  - **replicas:** The number of instances of the application to run for scalability and fault tolerance.
 - **desiredStatus:** The state in which you want the application to be. Common statuses include `Running` and `Stopped`.
-
 - **publicAccess:** Configures the public accessibility of the deployment. If enabled, the service will be accessible via a public URL.
-    - **enabled:** A boolean value that determines if public access is enabled (`true` or `false`).
-    - **urlPrefix:** The URL prefix under which the service will be accessible.
-
+  - **enabled:** A boolean value that determines if public access is enabled (`true` or `false`).
+  - **urlPrefix:** The URL prefix under which the service will be accessible.
 - **network:** Defines the network settings for the deployment, including the exposed ports.
-    - **ports:** A list of ports to expose.
-        - **port:** The external port number that will be exposed.
-        - **targetPort:** The internal port number the traffic will be directed to.
-
+  - **ports:** A list of ports to expose.
+    - **port:** The external port number that will be exposed.
+    - **targetPort:** The internal port number the traffic will be directed to.
 - **variables:** Defines any configurable parameters for the deployment. These are typically inputs or outputs such as:
-    - **name:** The name of the variable.
-    - **inputType:** The type of input, usually `InputTopic`, `OutputTopic`, `Secret`, or `FreeText`.
-    - **description:** A brief explanation of what this variable does.
-    - **required:** Indicates whether this variable must be provided (`true` or `false`).
-    - **value:** The default or specified value for this variable.
+  - **name:** The name of the variable.
+  - **inputType:** The type of input, usually `InputTopic`, `OutputTopic`, `Secret`, or `FreeText`.
+  - **description:** A brief explanation of what this variable does.
+  - **required:** Indicates whether this variable must be provided (`true` or `false`).
+  - **value:** The default or specified value for this variable.
+
+### Notes on Docker Image Deployments
+
+- **Mutual Exclusivity:** You cannot specify both `application`/`version` and `image` in the same deployment definition. Choose one approach depending on your use case.
+- **Image References:** Ensure your Docker image reference includes the repository and tag (e.g., `custom-repo/my-service:1.2.3`).
+- **Compatibility:** Direct Docker image deployments provide greater flexibility, especially for non-standardized applications or third-party containers.
 
 ### 3. Topics
 
@@ -112,14 +119,12 @@ topics:
 **Explanation:**
 
 - **name:** The unique identifier for the topic within your pipeline.
-
 - **persisted:** A boolean value that indicates whether the data in this topic should be stored persistently. Setting this to `false` means data will not be stored permanently and might be deleted after processing.
-
 - **configuration:** (Optional) This section allows you to fine-tune how the topic behaves. Common configurations include:
-    - **partitions:** The number of partitions within the topic. More partitions allow for greater parallelism but may complicate data ordering.
-    - **retentionInMinutes:** How long the data should be retained in the topic before being deleted or compacted.
-    - **retentionInBytes:** The total size of data that the topic can retain. When this limit is reached, older data is deleted.
-    - **cleanupPolicy:** Defines how the topic handles old data. `Delete` means old data is removed, whereas other policies like `Compact` could be used for different use cases.
+  - **partitions:** The number of partitions within the topic. More partitions allow for greater parallelism but may complicate data ordering.
+  - **retentionInMinutes:** How long the data should be retained in the topic before being deleted or compacted.
+  - **retentionInBytes:** The total size of data that the topic can retain. When this limit is reached, older data is deleted.
+  - **cleanupPolicy:** Defines how the topic handles old data. `Delete` means old data is removed, whereas other policies like `Compact` could be used for different use cases.
 
 ## How to Use the `quix.yaml` File