Add jq as dependency and remove json_extract (#4878)

**What does this PR aim to accomplish?:**

Adds `jq` as dependency and removes the now obsolete `json_extract` function.
`jq` is a small dependency and adds powerfull json abilities. With `FTL v6` we will have a whole new json-based API where `jq` might be needed anyway. Also for `PADD` to interact with `FTL v6`, `jq` will be a requirement: https://github.com/pi-hole/PADD/pull/247

---
**By submitting this pull request, I confirm the following:** 

1. I have read and understood the [contributors guide](https://docs.pi-hole.net/guides/github/contributing/), as well as this entire template. I understand which branch to base my commits and Pull Requests against. 
2. I have commented my proposed changes within the code and I have tested my changes.
3. I am willing to help maintain this change if there are issues with it later.
4. It is compatible with the [EUPL 1.2 license](https://opensource.org/licenses/EUPL-1.1)
5. I have squashed any insignificant commits. ([`git rebase`](http://gitready.com/advanced/2009/02/10/squashing-commits-with-rebase.html))

---
- [x] I have read the above and my PR is ready for review. _Check this box to confirm_

advanced/Scripts/updatecheck.sh

@@ -8,23 +8,6 @@
 # This file is copyright under the latest version of the EUPL.
 # Please see LICENSE file for your rights under this license.
 
-# Credit: https://stackoverflow.com/a/46324904
-function json_extract() {
-    local key=$1
-    local json=$2
-
-    local string_regex='"([^"\]|\\.)*"'
-    local number_regex='-?(0|[1-9][0-9]*)(\.[0-9]+)?([eE][+-]?[0-9]+)?'
-    local value_regex="${string_regex}|${number_regex}|true|false|null"
-    local pair_regex="\"${key}\"[[:space:]]*:[[:space:]]*(${value_regex})"
-
-    if [[ ${json} =~ ${pair_regex} ]]; then
-        echo $(sed 's/^"\|"$//g' <<< "${BASH_REMATCH[1]}")
-    else
-        return 1
-    fi
-}
-
 function get_local_branch() {
     # Return active branch
     cd "${1}" 2> /dev/null || return 1
@@ -61,19 +44,19 @@ if [[ "$2" == "remote" ]]; then
         sleep 30
     fi
 
-    GITHUB_CORE_VERSION="$(json_extract tag_name "$(curl -s 'https://api.github.com/repos/pi-hole/pi-hole/releases/latest' 2> /dev/null)")"
+    GITHUB_CORE_VERSION="$(curl -s 'https://api.github.com/repos/pi-hole/pi-hole/releases/latest' 2> /dev/null | jq --raw-output .tag_name)"
     addOrEditKeyValPair "${VERSION_FILE}" "GITHUB_CORE_VERSION" "${GITHUB_CORE_VERSION}"
 
     if [[ "${INSTALL_WEB_INTERFACE}" == true ]]; then
-        GITHUB_WEB_VERSION="$(json_extract tag_name "$(curl -s 'https://api.github.com/repos/pi-hole/AdminLTE/releases/latest' 2> /dev/null)")"
+        GITHUB_WEB_VERSION="$(curl -s 'https://api.github.com/repos/pi-hole/AdminLTE/releases/latest' 2> /dev/null | jq --raw-output .tag_name)"
         addOrEditKeyValPair "${VERSION_FILE}" "GITHUB_WEB_VERSION" "${GITHUB_WEB_VERSION}"
     fi
 
-    GITHUB_FTL_VERSION="$(json_extract tag_name "$(curl -s 'https://api.github.com/repos/pi-hole/FTL/releases/latest' 2> /dev/null)")"
+    GITHUB_FTL_VERSION="$(curl -s 'https://api.github.com/repos/pi-hole/FTL/releases/latest' 2> /dev/null | jq --raw-output .tag_name)"
     addOrEditKeyValPair "${VERSION_FILE}" "GITHUB_FTL_VERSION" "${GITHUB_FTL_VERSION}"
 
     if [[ "${PIHOLE_DOCKER_TAG}" ]]; then
-        GITHUB_DOCKER_VERSION="$(json_extract tag_name "$(curl -s 'https://api.github.com/repos/pi-hole/docker-pi-hole/releases/latest' 2> /dev/null)")"
+        GITHUB_DOCKER_VERSION="$(curl -s 'https://api.github.com/repos/pi-hole/docker-pi-hole/releases/latest' 2> /dev/null | jq --raw-output .tag_name)"
         addOrEditKeyValPair "${VERSION_FILE}" "GITHUB_DOCKER_VERSION" "${GITHUB_DOCKER_VERSION}"
     fi
 

automated install/basic-install.sh

@@ -330,7 +330,7 @@ package_manager_detect() {
         # Packages required to run this install script (stored as an array)
         INSTALLER_DEPS=(git iproute2 dialog ca-certificates)
         # Packages required to run Pi-hole (stored as an array)
-        PIHOLE_DEPS=(cron curl iputils-ping psmisc sudo unzip idn2 libcap2-bin dns-root-data libcap2 netcat-openbsd procps)
+        PIHOLE_DEPS=(cron curl iputils-ping psmisc sudo unzip idn2 libcap2-bin dns-root-data libcap2 netcat-openbsd procps jq)
         # Packages required for the Web admin interface (stored as an array)
         # It's useful to separate this from Pi-hole, since the two repos are also setup separately
         PIHOLE_WEB_DEPS=(lighttpd "${phpVer}-common" "${phpVer}-cgi" "${phpVer}-sqlite3" "${phpVer}-xml" "${phpVer}-intl")
@@ -360,7 +360,7 @@ package_manager_detect() {
         PKG_COUNT="${PKG_MANAGER} check-update | egrep '(.i686|.x86|.noarch|.arm|.src)' | wc -l || true"
         OS_CHECK_DEPS=(grep bind-utils)
         INSTALLER_DEPS=(git dialog iproute newt procps-ng which chkconfig ca-certificates)
-        PIHOLE_DEPS=(cronie curl findutils sudo unzip libidn2 psmisc libcap nmap-ncat)
+        PIHOLE_DEPS=(cronie curl findutils sudo unzip libidn2 psmisc libcap nmap-ncat jq)
         PIHOLE_WEB_DEPS=(lighttpd lighttpd-fastcgi php-common php-cli php-pdo php-xml php-json php-intl)
         LIGHTTPD_USER="lighttpd"
         LIGHTTPD_GROUP="lighttpd"