ACME: module configuration.

[bavshin-f5]

Module configuration directives only, no other functionality.
See the README.md file for currently implemented directives.

[bavshin-f5]

As Pavel suggested offline, changed syntax of the acme_certificate directive to acme_certificate issuer [identifier...] [key=...];, where an empty list of identifiers instructs the module to take the server_name values.

[avahahn]

The code looks great, with just a few caveats.

[avahahn]

In the nginx-wasm crate Pat used a static compile time assert to guarantee that manual access like that was correct before building. I think this crate's use of byte_offset also may call for something similar.

[bavshin-f5]

The general idea of configuration slot handlers in NGINX is that we don't know the exact type of the configuration structure, but we know that the value at conf + specified offset is of the necessary type. It's on the end user to set the right value in ngx_command_t.offset.
We could try to design a Command builder for the high-level Rust API better, but we don't have that right now.

The generic code looks unnecessary in the current context though, so I will remove byte offsets and replace with direct access to the structure fields.

[avahahn]

In the ACME module we are the 'end user' of this API. My concern was whether or not we can validate that we are fetching the right data structure. If we can predict the offset and type size at build time then I think it is worth the assert, but otherwise there is nothing we can do.

[bavshin-f5]

The only way to validate this that I can imagine is to generate the code to access the fields and never allow the user to interact with the offsets directly.
That would require proc-macros though, and IMO we aren't at the point where we should start introducing these yet.

[avahahn]

We can also generate code with the build script.
But if we can generalize it in the future with proc-macros, then maybe this is conversation for ngx-rust.... whenever you see proc-macros as ready.

[xeioex]

Otherwise looks good.

[xeioex]

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 773eaba..e7750c0 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -40,7 +40,7 @@ jobs:
           - master
           - stable-1.28
         build:
-          - debug 
+          - debug
           - debug-static
           - release
 
@@ -61,7 +61,7 @@ jobs:
             build: debug
 
     runs-on: ${{ matrix.runner }}-latest
-            
+
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
@@ -103,12 +103,12 @@ jobs:
         if: ${{ !cancelled() && steps.build.outcome == 'success' }}
         run: make BUILD=${{ matrix.build }} check
 
-      - name: run unit-tests 
+      - name: run unit-tests
         # always run if build succeeds
         if: ${{ !cancelled() && steps.build.outcome == 'success' && runner.os != 'macOS' }}
         run: make BUILD=${{ matrix.build }} unittest
 
-      - name: run tests 
+      - name: run tests
         # always run if build succeeds
         if: ${{ !cancelled() && steps.build.outcome == 'success' }}
         run: make BUILD=${{ matrix.build }} TEST_PREREQ= test
diff --git a/Makefile b/Makefile
index b39124a..250c0d2 100644
--- a/Makefile
+++ b/Makefile
@@ -106,5 +106,5 @@ clean: ## Cleanup everything
 build-%: ## Build with the specified configuration. E.g. make build-sanitize.
 	$(MAKE) build BUILD="$*"
 
-test-%: ## Test with the specified configuration. 
+test-%: ## Test with the specified configuration.
 	$(MAKE) test BUILD="$*"

trailing spaces

[xeioex]

LGTM.

[bavshin-f5]

Manually merged as af6fffb to clean the commit history.

Thanks a lot to all who participated in the review!