[4.0] Make meta description and meta keywords have defaults

[wilsonge]

• Fixes [4.0] Error saving articles with Publishing Options disabled  #26650
• Makes fields optional when creating articles in the API

Summary of Changes

Makes metakey and metadesc have default values of empty string in the table. Also means these fields aren't required for the API (so I've amended that test to reflect)

Testing Instructions

Disable the Publishing tabset from being displayed in component options. Try and save an article. Before patch you get a warning metakey is required. After patch article saves successfully.

Documentation Changes Required

None

[uglyeoin]

I have tested this item ✅ successfully on 28659b4

I have tested this successfully. Before there was an error on patch there was none.

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/26714.}

[richard67]

I have not tested this item.

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/26714.}

[richard67]

I have tested this item ✅ successfully on 28659b4

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/26714.}

[Quy]

RTC

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/26714.}

[wilsonge]

Thanks guys!