chore(deps): pin dependencies (#2)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| alpine | final | pinDigest |  -> `51b6726` |
| juanluisbaptiste/postfix |  | pinDigest |  -> `4f770a2` |
| koalaman/shellcheck-alpine |  | pinDigest |  -> `f73b035` |
| [pipelinecomponents/hadolint](https://gitlab.com/pipeline-components/hadolint) |  | pinDigest |  -> `430e949` |
| plugins/docker |  | pinDigest |  -> `2f15740` |

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Reviewed-on: #2
Co-authored-by: Renovate Bot <renovate@mgrote.net>
Co-committed-by: Renovate Bot <renovate@mgrote.net>

.woodpecker/build.yml

@@ -3,7 +3,7 @@ depends_on:
   - lint
 steps:
   selfhosted_tag:
-    image: plugins/docker
+    image: plugins/docker@sha256:2f157400c2cb7de1b309b0f044f119375108218e54d38e1340e00b9f93abdefb
     settings:
       dockerfile: Dockerfile
       repo: registry.mgrote.net/postfix
@@ -15,7 +15,7 @@ steps:
         - tag
 
   selfhosted_push:
-    image: plugins/docker
+    image: plugins/docker@sha256:2f157400c2cb7de1b309b0f044f119375108218e54d38e1340e00b9f93abdefb
     settings:
       dockerfile: Dockerfile
       repo: registry.mgrote.net/postfix

.woodpecker/lint.yml

@@ -10,7 +10,7 @@ steps:
           - tag
 
   hadolint:
-    image: pipelinecomponents/hadolint:0.25.9
+    image: pipelinecomponents/hadolint:0.25.9@sha256:430e949e6554d56ffc2dd08898ee609c71822d7fa1033f7c4dc240e90f2aac23
     commands:
       - hadolint Dockerfile
     when:
@@ -19,7 +19,7 @@ steps:
           - tag
 
   shellcheck:
-    image: koalaman/shellcheck-alpine:stable
+    image: koalaman/shellcheck-alpine:stable@sha256:f73b035c8ebfc8a66ba54e07af5cc41e790cf41fff45317914b1ce677dd9cada
     commands:
       - "find . -name *.sh -exec shellcheck {} +"
     when:

Dockerfile

@@ -1,5 +1,5 @@
 #Dockerfile for a Postfix email relay service
-FROM alpine:3
+FROM alpine:3@sha256:51b67269f354137895d43f3b3d810bfacd3945438e94dc5ac55fdac340352f48
 
 COPY run.sh /
 

docker-compose.yml

@@ -1,7 +1,7 @@
 version: '2'
 services:
   postfix:
-    image: juanluisbaptiste/postfix:latest
+    image: juanluisbaptiste/postfix:latest@sha256:4f770a2a6e1957ec45064826b64fbda0d2041729fe27774a7082a7646a63bd63
     expose:
     - "25"
     env_file: