feat!: allow setting default environment variable values (#185)

* chore: update dependencies

`time` has restricted the version of `serde` due to the addition of
precompiled blobs in the crate uploaded to crates.io.

See also serde-rs/serde#2538

* feat: add StringWithEnv type that expands variable values but stays a String

* feat: set default environment variable values if variable is unset

* fix: fix tests, add api docs

* fix: replace unmaintained atty with standard library

* chore: add deny, msrv to Makefile.toml

* chore: allow clippy lint

* style: run cargo fmt

* chore: disable lint that is no longer stable

* refactor: make EnvVarDefaults public

* refactor!: remove Deref impl for PileName

* chore: change checks used in check-all

* ci: add msrv and deny checks to CI

* chore: change TOML name from var_defaults to defaults

* doc: update book with environment variable defaults support

* chore: update sample config

* ci: delete problematic lines

* ci: fix job name

* style: fix clippy warnings/suggestions

* style: run cargo fmt

* chore: update dependencies

Author: Shadow53

.github/workflows/check.yml

@@ -11,7 +11,6 @@ jobs:
     outputs:
       rust: ${{ steps.filter.outputs.rust }}
       cargo: ${{ steps.filter.outputs.cargo }}
-      pytests: ${{ steps.filter.outputs.pytests }}}
     steps:
       - uses: actions/checkout@v3
       - uses: dorny/paths-filter@v2
@@ -39,6 +38,74 @@ jobs:
           # Push-only API key
           fossa-api-key: 7b6d2d5fb78bb718019e16184020ef6d
 
+  msrv:
+    name: Cargo MSRV
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Install stable toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          override: true
+          components: clippy, rustfmt
+
+      - name: Install cargo-msrv
+        uses: actions-rs/install@v0.1
+        with:
+          crate: cargo-msrv
+          version: latest
+          use-tool-cache: true
+
+      - name: Install cargo-make
+        uses: actions-rs/install@v0.1
+        with:
+          crate: cargo-make
+          version: latest
+          use-tool-cache: true
+
+      - name: Cargo msrv
+        uses: actions-rs/cargo@v1
+        with:
+          command: make
+          args: msrv-verify
+
+  deny:
+    name: Cargo deny
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Install stable toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          override: true
+          components: clippy, rustfmt
+
+      - name: Install cargo-deny
+        uses: actions-rs/install@v0.1
+        with:
+          crate: cargo-deny
+          version: latest
+          use-tool-cache: true
+
+      - name: Install cargo-make
+        uses: actions-rs/install@v0.1
+        with:
+          crate: cargo-make
+          version: latest
+          use-tool-cache: true
+
+      - name: Cargo deny
+        uses: actions-rs/cargo@v1
+        with:
+          command: make
+          args: deny
+
   fmt:
     name: Cargo fmt
     runs-on: ubuntu-latest