Adds test to test last refresh time

[Jerboa-app]

No description provided.

[github-actions]

Seems the coverage is below main by -1.26 %, please consider adding to the tests, thanks!
Here is the full report breakdown

Total coverage 22.44 % (-1.26 % against main)
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src/config.rs                     | 0.0   % 0 / 14
src/filesystem/mod.rs             | 0.0   % 0 / 0
src/filesystem/observed.rs        | 0.0   % 0 / 0
src/main.rs                       | 0.0   % 0 / 15
src/server/api/mod.rs             | 0.0   % 0 / 0
src/server/api/stats.rs           | 0.0   % 0 / 81
src/server/http.rs                | 0.0   % 0 / 20
src/server/https.rs               | 0.0   % 0 / 85
src/server/mod.rs                 | 0.0   % 0 / 0
src/web/discord/mod.rs            | 0.0   % 0 / 0
src/web/discord/request/mod.rs    | 0.0   % 0 / 0
src/web/discord/request/model.rs  | 0.0   % 0 / 3
src/web/discord/request/post.rs   | 0.0   % 0 / 10
src/web/mod.rs                    | 0.0   % 0 / 30
src/web/response/mod.rs           | 0.0   % 0 / 0
src/web/response/util.rs          | 0.0   % 0 / 16
src/web/throttle.rs               | 0.0   % 0 / 48
src/web/stats.rs                  | 4.45  % 11 / 247
src/content/resources/resource.rs | 20.0  % 3 / 15
src/lib.rs                        | 31.58 % 6 / 19
src/content/pages/page.rs         | 40.62 % 13 / 32
src/util.rs                       | 58.93 % 33 / 56
src/filesystem/folder.rs          | 59.26 % 32 / 54
src/filesystem/file.rs            | 72.73 % 24 / 33
src/content/resources/mod.rs      | 75.0  % 15 / 20
src/content/mod.rs                | 76.74 % 33 / 43
src/content/pages/mod.rs          | 88.89 % 16 / 18
src/content/mime_type.rs          | 100.0 % 25 / 25
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