borgmatic: improve support for version 1.8.0

The configuration file format of borgmatic has changed in version
1.8.0:
https://projects.torsion.org/borgmatic-collective/borgmatic/src/branch/main/NEWS

This commit makes Home Manager generate borgmatic's configuration file
using the new format.

Even though the NEWS file indicates that old configuration files are
compatible, this is not 100% the case: empty sections work fine in old
borgmatic but stop working in new ones. I've reported the bug upstream
by email as I couldn't create an account on the forge.

tests/modules/programs/borgmatic/basic-configuration.nix

@@ -62,50 +62,48 @@ in {
 
     declare -A expectations
 
-    expectations[location.source_directories[0]]="${
+    expectations[source_directories[0]]="${
       builtins.elemAt backups.main.location.sourceDirectories 0
     }"
-    expectations[location.repositories[0]]="${
+    expectations[repositories[0]]="${
       builtins.elemAt backups.main.location.repositories 0
     }"
-    expectations[location.repositories[1]]="${
+    expectations[repositories[1]]="${
       builtins.elemAt backups.main.location.repositories 1
     }"
-    expectations[location.one_file_system]="${
+    expectations[one_file_system]="${
       boolToString backups.main.location.extraConfig.one_file_system
     }"
-    expectations[location.exclude_patterns[0]]="${
+    expectations[exclude_patterns[0]]="${
       builtins.elemAt backups.main.location.extraConfig.exclude_patterns 0
     }"
 
-    expectations[storage.encryption_passcommand]="${backups.main.storage.encryptionPasscommand}"
-    expectations[storage.checkpoint_interval]="${
+    expectations[encryption_passcommand]="${backups.main.storage.encryptionPasscommand}"
+    expectations[checkpoint_interval]="${
       toString backups.main.storage.extraConfig.checkpoint_interval
     }"
 
-    expectations[retention.keep_within]="${backups.main.retention.keepWithin}"
-    expectations[retention.keep_secondly]="${
+    expectations[keep_within]="${backups.main.retention.keepWithin}"
+    expectations[keep_secondly]="${
       toString backups.main.retention.keepSecondly
     }"
-    expectations[retention.prefix]="${backups.main.retention.extraConfig.prefix}"
+    expectations[prefix]="${backups.main.retention.extraConfig.prefix}"
 
-    expectations[consistency.checks[0].name]="${
+    expectations[checks[0].name]="${
       (builtins.elemAt backups.main.consistency.checks 0).name
     }"
-    expectations[consistency.checks[0].frequency]="${
+    expectations[checks[0].frequency]="${
       (builtins.elemAt backups.main.consistency.checks 0).frequency
     }"
-    expectations[consistency.checks[1].name]="${
+    expectations[checks[1].name]="${
       (builtins.elemAt backups.main.consistency.checks 1).name
     }"
-    expectations[consistency.checks[1].frequency]="${
+    expectations[checks[1].frequency]="${
       (builtins.elemAt backups.main.consistency.checks 1).frequency
     }"
-    expectations[consistency.prefix]="${backups.main.consistency.extraConfig.prefix}"
-    expectations[output.color]="${
-      boolToString backups.main.output.extraConfig.color
-    }"
-    expectations[hooks.before_actions[0]]="${
+    expectations[prefix]="${backups.main.consistency.extraConfig.prefix}"
+    expectations[color]="${boolToString backups.main.output.extraConfig.color}"
+    expectations[before_actions[0]]="${
       builtins.elemAt backups.main.hooks.extraConfig.before_actions 0
     }"
 
@@ -120,7 +118,7 @@ in {
       fi
     done
 
-    one_file_system=$($yq ".location.one_file_system" $config_file)
+    one_file_system=$($yq ".one_file_system" $config_file)
     if [[ $one_file_system != "true" ]]; then
        fail "Expected one_file_system to be true but it was $one_file_system"
     fi

tests/modules/programs/borgmatic/exclude-hm-symlinks-nothing-else.nix

@@ -27,7 +27,7 @@ in {
 
     yq=${pkgs.yq-go}/bin/yq
 
-    hmExclusionsFile=$($yq '.location.exclude_from[0]' $config_file)
+    hmExclusionsFile=$($yq '.exclude_from[0]' $config_file)
     expected_content='/home/hm-user/.config/borgmatic.d/main.yaml'
 
     grep --quiet "$expected_content" "$hmExclusionsFile"

tests/modules/programs/borgmatic/exclude-hm-symlinks.nix

@@ -28,7 +28,7 @@ in {
 
     declare -A expectations
 
-    expectations[location.exclude_from[0]]="${excludeFile}"
+    expectations[exclude_from[0]]="${excludeFile}"
 
     yq=${pkgs.yq-go}/bin/yq
 
@@ -41,7 +41,7 @@ in {
       fi
     done
 
-    hmExclusionsFile=$($yq '.location.exclude_from[1]' $config_file)
+    hmExclusionsFile=$($yq '.exclude_from[1]' $config_file)
     expected_content='/home/hm-user/.config/borgmatic.d/main.yaml'
 
     grep --quiet "$expected_content" "$hmExclusionsFile"

tests/modules/programs/borgmatic/include-hm-symlinks.nix

@@ -28,7 +28,7 @@ in {
 
     declare -A expectations
 
-    expectations[location.exclude_from[0]]="${excludeFile}"
+    expectations[exclude_from[0]]="${excludeFile}"
 
     yq=${pkgs.yq-go}/bin/yq