@spec blank_to_nil(value) :: value | nil when value: term()

Returns nil for nil or blank-string inputs; passes non-blank strings through unchanged. Useful when reading query params, form values, or settings where empty string and nil should mean the same thing.

Non-string values (e.g. a list from a key[]= query param) pass through untouched — the helper only collapses the empty string, it never raises on unexpected input.

iex> PhoenixKit.Utils.Values.blank_to_nil(nil)
nil
iex> PhoenixKit.Utils.Values.blank_to_nil("")
nil
iex> PhoenixKit.Utils.Values.blank_to_nil("hello")
"hello"
iex> PhoenixKit.Utils.Values.blank_to_nil(["a", "b"])
["a", "b"]

@spec presence(term()) :: nil | String.t()

Like blank_to_nil/1, but trims whitespace before the blank check.

Returns the trimmed string when there's content, nil otherwise. Use this for inputs where leading / trailing whitespace shouldn't count as "present" (HTML form values, URL query params that may carry stray whitespace, scraped IDs, etc.). When the value will already be normalised by the caller, prefer blank_to_nil/1 to avoid the unnecessary String.trim/1.

Non-string values (e.g. a list from a key[]= query param) yield nil — the helper treats anything that isn't a non-blank string as "not present" rather than raising on unexpected input.

iex> PhoenixKit.Utils.Values.presence(nil)
nil
iex> PhoenixKit.Utils.Values.presence("   ")
nil
iex> PhoenixKit.Utils.Values.presence("  hello ")
"hello"
iex> PhoenixKit.Utils.Values.presence(["a", "b"])
nil