feat: move mgcv to Suggests

DESCRIPTION

@@ -1,7 +1,7 @@
 Type: Package
 Package: openairmaps
 Title: Create Maps of Air Pollution Data
-Version: 0.9.1.9003
+Version: 0.9.1.9004
 Authors@R: c(
     person("Jack", "Davison", , "[email protected]", role = c("cre", "aut"),
            comment = c(ORCID = "0000-0003-2653-6615")),
@@ -25,7 +25,6 @@ Imports:
     leaflet (>= 2.2.0),
     lifecycle,
     lubridate,
-    mgcv,
     openair (>= 2.13),
     purrr (>= 1.0.0),
     rlang,
@@ -39,6 +38,7 @@ Suggests:
     httr,
     jsonlite,
     knitr,
+    mgcv,
     mirai,
     prettymapr,
     rmarkdown,

NEWS.md

@@ -6,8 +6,12 @@
 
 * The progress bar shown when `progress = TRUE` now better reflects the actual time until function completion.
 
+## Refactoring
+
 * `{ggplot2}`, `{ggspatial}`, `{prettymapr}` and `{ggtext}`, the packages which support static mapping, have been moved to `Suggests` from `Imports`. This gives the package a smaller size for users who only use `{openairmaps}` for interactive mapping. On first trying to use a static mapping function, users will be prompted to install these packages.
 
+* `{mgcv}` has been moved to `Suggests` as it is only used in one place (`trajLevelMap(smooth = TRUE)`)
+
 # openairmaps 0.9.1
 
 ## New features

R/traj_trajLevelMap.R

@@ -446,6 +446,7 @@ trajLevelMapStatic <-
 #' Smooth grid for trajectories
 #' @noRd
 smooth_trajgrid <- function(mydata, z, k = 50, dist = 0.05) {
+  rlang::check_installed("mgcv")
   myform <-
     stats::formula(stringr::str_glue("{z}^0.5 ~ s(xgrid, ygrid, k = {k})"))